If you get a boat with a new motor it's all about maintaining it properly. If you buy a used motor, have a good mechanic that you trust look it over. If you don't know one, good luck. You never know how someone treated it.
I got mine new in 06 with a 4 stroke Yamaha and have never had an issue. Hasn't cost me a dime aside from normal maintenance
If you cant afford a new boat motor trailer combo forget it. Plus 7 people on a boat is a disaster, unless you want to get rid a few of them. Get a kayak. No mechanical problems, and you'll become a better waterman, instead of another chenk of human cholesterol clogging up the water way and clueless at that. But good luck and have lots of fun :-)