"A co-founder is your strongest and greatest validation."

No. A customer is your strongest and greatest validation. The only thing that proves people will buy what you're selling is someone buying what you're selling. Any other "validation" is mere vanity. You're just enjoying people agreeing with you. Clue: They might be entirely wrong.

I'm sorry, but I think validation of an idea is probably one of the worst reasons to get a co-founder I've heard.