The big question here is how many of these will you do, and will you be able to be a real co-founder to them. Doing one would be great. I could maybe even see up to 5 or so, since there's going to be an attrition rate on the people getting to MVP -- maybe a deal where if you decide not to go forward, they keep the $5k and 98% of the business?

I have no idea who you are, but if someone who seemed to be a credible cofounder offered to do a startup, front $5-8k, and do sales/dev/etc., that could be an entirely reasonable deal for some people.