I've seen folks come in at 39, it is what it is. If you don't have kids or a spouse they're still gonna make you live in the dorms though.
Nothing wrong with joining but it's prolly best to have a reason: need a job, wanna serve your country, GI Bill, something. Joining just to join so you don't say "I wonder what if" prolly isn't the strongest reason, and there will be situations where you're gonna need to have a "Why?" to get you through.
If you can pass the physical, won't need waivers, and aren't picky or unrealistic about your AFSC, go talk to a recruiter. Maybe you join the Guard: still get the same benefits, they have full-time positions available, and you won't have to move if you join in your state.