Need help RE house I still own with XH

[trafficgirl]

I need some help figuring things out, so I'm turning to the SO board. And sorry this is so long.

Backstory:
XH and I still own our former marital home. We are way underwater on it (bought it at the height of the market) and neither one of us could afford to keep it on our own, so at the time this was our only choice.

XH moved out and I lived in it for about a year, paying the majority of the mortgage. Then I moved out as it was putting me into debt to live there by myself and it was in a bad location to try and rent a room to someone. It also needed (and still needs) a ton of repair b/c we didn't do a good job taking care of it when we lived there (which is on us). Then when I lived there by myself I could hardly stand being there so I didn't do a good job of taking care of it either.

Current Day:
XH's brother and SIL are renting the house from us. We charge them about half of what the mortgage is in exchange for them doing improvements on the house (the brother went to carpentry school). XH and I agreed that we'd pay for materials and they would do the labor.

There are both major and minor things that need to happen to the house to hopefully one day sell it (or at least rent it to cover most if not all of the mortgage). Most of the minor and some of the major things the brother and SIL can do. Here's the problem - XH never has any money to contribute to doing improvements. He owns a secondary house (which I'm not invovled with) that he says has to come first. But I'm not about to pay for improvements by myself because I'll never get reimbursed. We're talking thousands of dollars here, not just a couple hundred.

I'm very tempted to tell him - hey, your money problems aren't my problem and you either need to figure out a way to contribute to improving this house or the house needs to go into foreclosure.

I've also looked into doing a shortsale, but there are so many improvements that need to be done before it's anywhere near ready to go on the market that I don't think it's worth it. I'm trying to avoid having to deal with this house (and XH) for the next 10 years. This is the last thing tying us together.

Thoughts? What should I do here? I haven't looked too much into foreclosure and how that would affect me (other than effing up my credit score for 7 years), but right now having a bad credit score sounds better than dealing with XH and the house for the next decade.

Any advice or similar situations would be appreciated. Thanks ladies.