Another thought that may matter depending on how you want your altruism to work. An old guy left land to his kids with the requirement that they couldn't profit off it as he loved nature. The kids did it anyway and made tons of money. I found out after that he should have included the conservation authority as an owner as well and they would then fight to maintain his wishes. If your altruism is supposed to help maintain affordable housing in perpetuity, you may want to include a quality charity in the deal (Out of the cold?). Obviously, for better or worse, that limits the ability of the buyer to flip it on the way up the property ladder. A 900 sq ft warm, dry and safe condo is not a bad endpoint to the property ladder though.
Another option (but I don't know if it exists) is a charity that tries to maintain a distributed stable of affordable rental properties. Donate the condo to the charity for the tax write-off and they now have housing for another family in perpetuity (theoretically, they could rent out for as low as maintenance+utilities+property tax+insurance+contingency as their cost of acquisition/carrying was zero). Hell, maybe you spin up the charity. I would set the rent up like I said but include a mandatory saving component and time limit. If you did $250/mo savings and four year limit? At the end of the four years, they get their 16K back to be used to have a chance at a stable future (could the charity hold it, invest it and release it when they get CPP?). Getting the details right is complicated but it could provide a path to help people that would not have any retirement income other than CPP (which is crap).