Mobile printing and personal wifi question. iPhone

I am sorry if this is in the wrong spot but it involves a few different products. My issue is that I want to be able to print in my vehicle from my ipad to a printer. I know bluetooth is not supported so I was wondering if a personal wifi can be set up from my iphone to allow the wireless printer and the ipad to work together. I have an iphone 3gs currently. I will upgrade if needed to the iphone 4. Please help and if you have any suggestions to be able to do this another way, let me know.
Fyi: I do onsite estimates and do not have the luxury of a wireless network all the time. iphone and ipad both have data plans.
I-mac Mac OS X (10.6.4)