It sounds like a brand-new startup business that isn't properly established yet - hence the lack of a local office, and the fact that he spent the whole interview trying to pitch his business idea instead of interviewing a potential employee.
If you need the cash & there aren't any penalty clauses in the contract that will prevent you from getting out when something better comes along, I'd go for it. After all, you're working from home mostly & it'll fill in the gap on your CV. And who knows? If this new business takes off, you could be in line for a better position (and more pay) further down the line.
It could also be that this is a fly-by-night operation who're developing some software in the hopes of selling it on, and if that's the case then there's a chance you won't get paid if they don't find a buyer. So only go for it if you think it's worth taking that chance. After all, Bill Gates took the same sort of chance.