One awesome thing about IPT is the serious cash savings. The average traditionally diapered baby goes through 5,000-8,000 diapers before being potty trained, which adds up to around $1,600-$2,300. Cloth diapering be expensive too, with costs between $800-$1,100 (source: http://www.surebaby.com/costs.php). Multiply these costs by how many children you plan to have, and we're talking about a load of money.
You have several choices with IPT, but you'll save no matter what!
Disposable diapering was the best option for us with our first baby, because we had no idea what kind of success we'd have with IPT. After we started IPT, the amount of diapers we were throwing away dwindled down to one or two a day very quickly. We soon found we could buy the cheapo brands from Wal-Mart, because when my son did have an accident, it was small compared to how a baby normally wets or soils a diaper. Disposables are very convenient, just throw them away when dirty. But that's the downside too. You're throwing your money down the drain. Even so, by doing this even part time, you're cutting down on the diapers you're using, which means you are saving cash. One downside is that disposables feel dry even after your baby pees in them, which can make a baby lose some awareness of when they are peeing.
Cloth diapering can be as expensive or as cheap as you want it to be. From using a diaper service to buying used flat folds, there's a whole world of options for you. The initial investment in cloth diapers is a bit more than for disposables, but they quickly pay for themselves. With our second baby, we've decided to do cloth only, using disposables on those rare occasions when I fall behind on the laundry. (= We have found that she seems to have more awareness and fewer pee misses when in cloth. She has fewer accidents than her brother did at this stage, but that could be due to the differences in personality or gender. In all we have about 10 pocket diapers with microfiber inserts that we use for her, with maybe a total of $100 spent. And those diapers can be used on any future babies we may have! Our favorite ones are the BumGenius 3.0 found here in my Amazon store. They're well made and we haven't had leaks with them.
There are people who have had enormous success being completely diaper free. In fact, in most non-Western cultures they don't use any diapers at all, while still being very hygienic. Unfortunately, I'm one of those people who get too stressed out about possible misses on furniture or carpets. It's kind of ironic though, because I house trained a dog once without the use of any diapers, and we were different species!