Some historic homes in no-so-great states of repair can be great investments, if you’re willing to put the additional time, sweat equity and money into them. However, because of their age, historic homes can be costlier to fix and renovate than newer ones. You may find that generations of homeowners have made repairs and additions with varying levels of expertise, and old walls can hide some big surprises.

If you’re thinking about buying a historic home, you need to make sure you’re up for the challenge — financially and emotionally.

We tracked down six homeowners who have taken on these projects and asked them to share the lessons — good and bad — that they’ve learned along the way.

Meet the panel:

Ron Tanner, a professor at Loyola University-Maryland, bought an 1897 townhouse in Baltimore in 2000 with his wife (then-girlfriend), Jill. The house had most recently been occupied (and vandalized) by a fraternity. The couple spent 15 years restoring it, documenting the project on a blog and in a book, “From Animal House to Our House: A Love Story.” They’re now restoring an 1880 farmstead about 40 miles from Baltimore.

Amy and Doug Heavilin are currently restoring a 1902 Victorian-style house in Franklin, Indiana. They had already worked on homes from the 1920s and 1930s, and were living in one from 1875 when their current home — their “dream house” — came on the market after a foreclosure. You can follow the Heavilins’ projects on their website.

Ken Roginski‘s restoration of a 1910 late-Victorian-style home in Freehold, New Jersey, led him to a career change from finance to historic preservation. He has worked for the New Jersey Historic Trust and is now a consultant — “The Old House Guy” — helping other owners of historic properties with their projects.

Alex and Wendy Santantonio bought a 15-foot-wide 1885 row house in Old Town Alexandria, Virginia, in 2003 and are still finding projects that need doing They’ve also purchased a 1908 beach house in Maryland and are continuing to document their restoration projects on their website.

Click ahead to see 10 things these homeowners have learned and for before-and-after photos of some of their projects.

Pro: You’re protecting your community’s history

All of the homeowners we spoke with agreed that restoring a house brings value that can’t be measured in dollars and cents.

“People have a connection to this house,” Amy Heavilin said. “People knock on our door and tell us about when they lived here. It was broken up into apartments at one point. So a lot of people lived here, and they bring photos when they come to visit. The history of the people who lived here was amazing.”

“We’re not just restoring it for us,” she said. “We’re restoring it so other people can continue to love it.”

Con: Historic designations may limit some of your choices

If your home has a historical designation or is in a historic district, you may have to follow certain rules when making changes to the exterior.

The Heavilins were already planning to keep a historically accurate color palette on the home’s outside, but the local historical society did hesitate when considering their plan to turn a back porch into part of their new kitchen.

“There were windows about a foot above the floor, and when we wanted to move those windows so we could put cabinets in, there was a little pause,” Amy said. “But they decided that because [the porch] was an addition and not part of the original house, it wasn’t a problem.”

“If we had wanted to change a window on the front of the house, they probably would have said that wasn’t allowed,” Doug said.

Pro: You’ll learn a lot

The Heavilins admitted that they didn’t have a lot of home-repair experience going into their first old house, but they’ve picked up a lot of skills along the way.

“We’ve learned how to do so many things, and I don’t want people to be scared of a project and think they can’t do it,” Amy said.

“It’s easy to get overwhelmed, but you’re not the first to take on a project like this,” Doug added. “People take these on and are able to get it done.”

Con: Your project will probably take longer and cost more than you expect

Another point on which the homeowners agreed is that your project will almost definitely take longer than you expect.

“I thought we’d be done in two years,” Ron Tanner said. “I had this optimism, and I kept repeating to myself: ‘Just two more years, just another two years.’ I couldn’t surrender that optimism, and it drove me.”

In the end, the Tanners’ renovation took 15 years.

They started with a bank loan to fund some of the immediate repairs like replacing the roof and plumbing, refinishing floors and making electrical repairs. But they had to slowly save up for additional costs like custom-made, hand-turned balusters to replace the ones the fraternity brothers who previously lived in the home had knocked out with baseball bats.

Con: You may have to sacrifice some creature comforts

During the renovations, you’ll have to put up with a lot of mess and maybe have to give up some of your home’s normal amenities.

While the Heavilins said they were able to go without a functioning kitchen for four or five months, the Tanners’ situation was more extreme.

“We were basically living in squalor for years, living with broken and damaged things for years,” Tanner said.

Tanner advised homeowners to create at least one “safe” room during their project where they can escape from the renovation madness. It doesn’t have to be a finished room, but it should be clean and free of tools and building supplies.

Pro: You get immediate gratification from the work

Finishing your home may take years, but the immediate gratification you get from seeing the progress you’ve made is a great feeling, Tanner said.

“It’s incredibly exciting to watch it come together piece by piece,” he said. “For example, you spend the day weeding and when you look around you think, ‘Wow, this is looking pretty good.’”

Con: Contractors can be hard to find

Sure, plenty of contractors are in the phone book, but that doesn’t mean all of them have the skills and expertise to help you with a historic renovation, Ken Roginski said.

“The biggest con is finding somebody to do the work,” he said. Homeowners should seek out a contractor who specializes in historic restorations. These contractors are more likely to know how to repair what’s already there, rather than tearing out impossible-to-replace features like plaster and antique windows and replacing them with newer, flimsier versions.

Roginski has compiled a list of resources on his blog and said other historic home forums and websites also have information on contractors and specialists from around the country to assist homeowners in finding help in their areas.

Pro: Historic districts could protect your home’s value

If your home is located in a historic district, it may retain its value better than if it were located in another part of town, Roginski said.

The rules historic districts have in place for the external appearances of homes mean your neighbors won’t be able to add any unsightly additions to their homes and lower the surrounding property values.

“If all the houses in the neighborhood are going to look really good, your home can be worth about 20 percent more in a historic district,” Roginski said.

Con: What you’ll find behind the walls is anybody’s guess

You never know what you’ll find behind the old walls of a historic home.

Alex and Wendy Santantonio were in their home for about a year-and-a-half before they learned they had some serious structural problems: There were termites, they had water damage and an addition on the back of the house had been built without a foundation.

Through the years, a lot of people in most historic homes have been making repairs and “improvements” of sometimes-dubious quality. That’s why it’s so critical to hire a good home inspector to look carefully at an older property before you buy. Ask yourself whether the time and money it will take to address necessary repairs are really worth your while.

“I think with all houses, and particularly an old house, you’re always going to uncover something you weren’t aware of, even after the inspection,” Wendy Santantonio said. “I wish we had been better prepared for that emotionally and financially.”

Pro: There’s an extensive community of people willing to lend their support

“When we bought our home in 2003, the [online] old house community was there, but not nearly as mature as it is now,” Alex Santantonio said. “The online community has filled out. There are forums where anybody can ask questions and get a bunch of different opinions from people who have been there and done that.”

And it’s not just DIY-ers joining the conversation.

“On these old home community websites, quite a few contractors contribute often,” he said. “They’re not necessarily trying to get work, either. They really have an interest in helping people accomplish their projects.”