You have to make a complex-retractable available such as a Cessna Cutlass RG for pattern work, otherwise the air work can be done in any typical trainer. Obviously changing airplanes during a checkride is not feasible to save a few bucks, so most people take the entire ride in a retractable. By the time you go for your ride this rule may change as there is a "notice of proposed rule-making" by the FAA to remove the retractable aspect of the definition of "complex" airplane. Make sure to check on that before starting your training and checkride. Getting a CFI is not all that expensive. Go through a Part 61 school. I had maybe a couple of grand into it before mine was done. It's mostly about knowledge- not so much about your flight proficiency; because you have already learned to do all the practical tasks. Buy yourself a flight library and read it thoroughly and take people out to the practice area and teach them to do things. You'll need a spin signoff, and in my opinion you should have a tailwheel signoff as well.