I use AP racks exclusively and I love them. I currently have 4 AP racks and will be ordering another one shortly. They are well worth the money and your snakes will do great in them. I have never used a home made rack but I know alot of people do and they work great. For me it was more for the uniform look of the rack and you know what your getting. If you need the rack in the next few days I would maybe say look into Reptile Basics racks as they are very good too. AP generally takes about 6-8 weeks to have the rack available and Reptile Basics is more like 7-10 days. Either way you cant go wrong. Hope this helps you out. Wich ever way you decide you will be happy and your snakes will do very well in a rack.
As for a thermostat I would recommend a spyder-tronics Herp stat. I use these for all my cages and racks and love them. All depends on what you are looking to spend on it all.