... I really did not realize that there was so much 24 volt stuff available for inside the house part of the bus. I will research the appliances and all the other parts i need for inside.
Just to save you some time and frustration: you will not find any "24-volt light fixtures."
For incandescent lighting, basically, a fixture is a fixture -- you buy 12-volt fixtures, and, if they have bulbs in them already, you toss the bulbs and replace them with 24-volt models. Almost every style of 12-volt incandescent bulb also comes in 24-volt, however there is usually a price premium. Finding the bulbs takes a bit of research, but they are widely available on the internet (shop around, prices vary considerably). Like Jim, we have quite a few of the projector-lamp style (MR-10 or MR-16) fixtures, which we have on low voltage tracks. We run all of it at 24 volts.
If you prefer LED lighting, you again buy those in 12 volt models, but buy them in pairs, and wire each pair in series. Just make sure that you wire together only pairs of identical lights.
Fluorescent is another story. Here you will need to find fixtures with 24-volt ballasts, or use 120-volt models (much cheaper anyway) and run them from your inverter, or run 12 volt models on 12 volts from the battery center tap, with an equalizer.
For water pumps, FloJet and Jabsco both sell a more or less identical 4.5 GPM variable-speed pump that works on 24 volts (or 12, it's a multi-voltage item).
Most of the low voltage marine refrigerators now use the Danfoss compressor system which is also dual voltage and works on either 12 or 24.
FanTastic fans, LP alarms, and the control boards of RV-style appliances like LP water heaters and absorption refrigerators are all 12 volts -- you'll need to run those from the center tap. Again, an equalizer is recommended to keep the batteries discharging/charging evenly.
To answer your question about what inverter we chose, here is a link to our construction web site, with way more detail than you ever wanted to know about our electrical system, including all the specifications, drawings, and diagrams:http://ourodyssey.us/bus-conversion.html
(scroll down to "Odyssey's complex electrical system")