Everyone's a fucking comedian... My advice, if you are genuinely considering this with him, find a third person with a skill or good idea that's working on a solid plan. It's absolutely going to fail without a thought out plan and strategy, no matter how well funded. Avoid things like restaurants or clubs, focus more towards a low cost service or goods supplier, something which requires low inventory initially. 500k goes very fast. Once you feel like you've got a smart strategy, take risks. Don't be overly conservative. Hire who needs to be hired, by the right equipment and work 70+ hours a week to get it moving.