How many times have you driven past a fixer-upper and said to yourself, “I bet I could get that place cheap! And then I could slap a coat of paint on it, do some repairs, and have a real nice house?” I do it all the time. I like the thought of turning a so-so home into my own miniature palace and saving money doing so.

But, as I have to remind myself, there are plenty of ways that scenario can go very wrong. There are plenty of opportunities for a renovation to suck up your time and money — and still leave you with a less-than-great house.

Just what are the hidden costs, though? While every house is different, each time I talk to someone who’s done their own renovations, certain similar themes pop up:

• Plumbing. In many states, homeowners aren’t even legally allowed to work on their own plumbing — they have to call a professional. And, honestly, that’s not a bad idea. While I don’t like the idea of the government telling what I can and can’t do, plumbing is problematic. When something goes wrong with a house’s plumbing, it generally goes bad in a big way: even a small leak can mean that a wall rots and needs replacement, not a cheap proposition.
• Time. For many homeowners, the amount of time necessary to do home renovations on their own is prohibitively costly. There are a certain number of hours that have to go into doing renovations, no matter how you do them. There’s also the question of the value of your time: can you make more money working an hour than it costs a contractor to work on your house? If so, financially, it may just not make sense to do a lot of the work yourself.
• Paperwork. You’re just doing some rewiring on your house, or maybe building on an addition, right? There’s no paperwork involved, right? Wrong! Depending on just what renovations you’re doing and where your home is, you may need a building permit, an inspection, or some other bureaucratic paperwork. Taking care of permits and fees can add up quickly in terms of both time and money, especially if we’re talking about a big renovation project. And if you don’t take care of all the necessary paperwork, you may have to worry about a fine.

If you’re considering doing home renovations on your own — especially if you’re buying a house expecting to do some work on it — take the added costs into account. You should be thinking about more than the cost of materials and work: what happens if something goes wrong? That ‘if’ may very easily turn into a ‘when’ if you don’t have much experience with renovations, especially with more skilled work like plumbing.