I have been going through the same considerations about buying a sand blaster. Here are several tips I have come across from different sources:

1. Do NOT use an oiler
2. Use different hose, from sand blaster to gun, than the one you will be using for painting. Make sure hose ID is sufficient to deliver required amount of air at desired pressure. A multiple steel braid hose is best but expect it to wear as media passes through it.
3. Pressure type sand blasters are faster because of increased speed they produce in the blast media. Most can handle all types of media
4. Syphen type (non-pressurized and usually lesst than $100) do not produce the "hitting power" to get most jobs done in a reasonalbe amount of time. May not be able to handle all types of media.
5. Seclect blast media according to material to be removed and base material. Some media will remove rust but not paint. Others will remove rust and paint.
6. Keep blast stream moving on thin metals to reduce heat buildup and warping. Different blast media creat different amounts of heat.
7. The smaller the air storage tank, the more the compressor will cycle.
8. Wear full protective cloting, including gloves, ear protection and head & face cover.