Let me start by saying I started about where you are height and weight-wise--close enough the differences don't matter.
I would suggest getting a cheap road bike and sticking with your buddy for now. Two riders means a lot more motivation, a little healthy competition, and if you are riding to lose weight, it is a lot better to have a partner who can tell you to get off your butt when you don't want to and vice versa.
Also, off-road riding can tend to be burst-riding: blast over an obstacle, go easy to catch your breath before the next obstacle. Not as good for weight loss (tons of fun though.) Also, off-road is more a full-body workout---you need to lift the bike a lot. If you are heavy and not too fit, you will find that a real chore.
Once you lose some weight and gain some fitness, off-road will be come Loads more fun.
Also, when you are heavy, you are asking a lot of the suspension and it simply cannot work as well. So, you either need to buy a much more expensive bike ... or wait until you are a little lighter.
In any case, a cheap full-suspension bike is not recommended. if you are spending less that about $1200 you are basically buying headaches and weight, not suspension.
The same figure might be half that for front-suspension only.
And a big guy (or girl) on a cheap F/S bike is just a series of expensive mechanical failures waiting to happen, unfortunately probably not interspersed with fun rides. too big a rider on too cheap a shock and ... it just won't be fun.
For several hundred dollars you can buy a very decent brand-new road bike and share the miles with your buddy. Maybe you will like it and not want to go off-road. if you still feel the urge, you will enjoy it a lot more because you will have the fitness.
Even so, if you plan to rice actual trails, where you will be slamming rocks and roots and maybe getting a little altitude, forget cheap suspension. For anyone much over 200 lbs, it would be wiser (IMO) to spend a little more to get a little more. N one enjoys blowing a seal on their shocks.
(by the way, I went with a n almost -new used F/S bike which was worth (new) a lot more than I paid for it. It was an accidental Craigslist find ... but maybe stop in on CL every now and then ... it is like that one-in-a-million Ferrari in a barn ... if you happen to see it the one day it is for sale for way less than it is worth, you will be psyched for years.)