I would ask about who does the lasering, what their qualifications and training are, etc. There are few regulations in the industry and some dodgy people around, unfortunately. I go to a place run by a doctor, which is more reassuring to me. personally I would only get it done from someone with medical training. That's not to say that it can't be done well and safely by someone else, it's just an extra degree of security.
I also wouldn't pay in advance - you don't know how many sessions you'll need to begin with. Also, they like you to come back every month, but it can often take a bit longer than that for the hairs to grow back and the treatment only works when they're in growth mode, so you may find 6-7 weeks works better. This is what my doctor told me, so I have tended to go at 6-8 week intervals.