Working in air ambulance has its ups and downs however to make it a career is a bit sketchy. Like the previous post mentioned it is feast or famine, there are times when you'll have three or four flights back to back and times when you'll go 4 days with out a transfer. Fixed wing air ambulance is sort of at a disadvantage since the helicopters are the bread and butter of air ems.
Most company's including the one I work for do 12 hour shifts and you flip flop every other work stint between day and night shift. Unlike the previous post above the company I work for does 12 days on 6 days off. Kodia I notice that you posted in the regional section a couple of times and are looking to go the airline route perhaps? Fixed wing air ems can be fun and definately rewarding however time DOES NOT come quickly if this is a time builder for you. There are a few companies that do have gov't contracts to transport via fixed wing like Eagle Med out of kansas but besides that its back to feast of famine.
Over all it is a fun career and the experience is that like no other however. you reach a plateau after a while in pay and equipment, this is the downside. It seems to me that this may be a temporary job for a few years until the economy turns around for you and if this is the case then by all means I say go for it. On the contrary if this is going to be the support system for you and your family for years to come I would weigh my options carefully.
Look into Eagle Med(Ballard aviation, Kansas), Eagle air med(Utah), Life Flight, midwest lifeteam, Mountain LifeFlight(cali) just to name a few. On the bright side all the air EMS services that I know of are part 135 which gives you an advantage if you want to stay in the corporate world or even transition to the 121 world.
Good luck my friend and PM me if you have any further questions