Jules: In my experience, there are two kinds of RFPs ...
1. Help me with my books: These RFPs will be QB 99% of the time. It will involve logging into their computer remotely and maintaining their books, or swapping the QB file back and forth, or otherwise sharing the QB file in some way.
2. Do my books for me: These RFPs want you to take over the bookkeeping. For these RFPs, you can use whatever you want, as the client will never have their fingers in the mix. If you want to use Peachtree, they won't care
If you stick to the second type of RFP, you'll be fine! Also, those types of jobs typically entail more hours/week, so they could be better contracts anyway
Deb