[tmetzner]

I'm a big fan of transparency. I'd explain the situation and let them know that you believe what you now own is valuable, but that you're happy to give them the first rights to (whether they hire you or not).

Could offer it as a deal sweetener if they do work with you, but also just offer to sell it at a reasonable price if not. Truth is today it's prob not much more valuable than what you paid for it, otherwise you wouldn't have been able to get at that price.