I can think of many risks. It must some kind of special name for you to even contemplate a 'lease to own' domain name situation.
If it were me, I'd go a different route. I'm no pro, but in general terms, in a rent to buy or lease to own situation, the other party retains the title or rights until ALL your obligations are met.
So you could build up a site with someone else having the authority down the line to inform you that Oh, so sorry, you've failed to meet the terms of the lease and therefore your lease on whatadomainname.com is being terminated and you may no longer use the name.
martinibuster, nice find. ;-) Just kidding. Yes, this question has something to do with my previous post. But I don't think it's the same. I mean, in the post before I was asking about possibilities to acquire a domain name besides buying and a lease-to-own arrangement. Now I just got a specific question about a lease-to-own arrangement. Well, I didn't mean to be uncool. Sry.
kevinpate, thank you for your response. That's exactly what I wanted to know. Well, I guess, doing a lease-to-own arrangement is by far not as secure as registering your own domain. That would be really crappy if you lose your domain after you already did promotion and other thing.