I've run out of money, so I can't afford a gym membership or a power rack. What can I do with what I have?

I had planned on Starting Strength, but then the money went poof. I've been following this plan, but I've maxed it out on my 40lb (2x20) dumbbell set. Before the money ran out I bought a bench and a 100lb weight set to get started, but now I'm not sure what to do with it. The squats seemed pretty essential, but I don't know of a way to do them safely.

I'm a super noob, so please keep that in mind. I'm currently 250lbs, at 5'11".

Edit: Whoops, should note what I'm looking for, shouldn't I? I need a way to progress from the current plan since I can't go right into SS. If it's possible to only replace the squat for something else and retain the rest of the program without the rack, that's great, and I'd love to hear opinions about it.