Curious about purchase option agreements

[John Divine]

Hey BP, I'd like to learn more about a purchase structure I don't hear about often: just a straightup option to purchase or purchase option agreement (NOT a lease option). 

In my mind, the agreement would look loosely like this: The option buyer pays an upfront fee to the option seller, giving the buyer a right to buy the property at any time between now and a certain date in the future, for a set price. I'm interested ideally in very long-dated contracts to take advantage of appreciation. So for example, you give the seller $5k upfront in exchange for the right to purchase a property (let's say worth $200k today) for $250k in ten years. The seller keeps that $5k no matter what, and it's not credited back at the time of sale. If you're familiar with stock options, this is exactly how call options work, although they only go out a max of maybe 27 months or so.

My questions are a bit numerous, but I've ordered them roughly in order of importance for me: 

-Is this legal? If so, has anyone out there done this and how did it go?

-Are there legal restrictions on this in NC, such as the length of the option?

-What sort of protections can be put in place for the buyer? I'm thinking of liens, backtaxes, making sure the seller doesn't sell to someone else, etc.

-Do folks have ideas about the best ways to source (i.e. find an option seller) for such deals?

-If these sorts of deals are doable (preferably in NC, but I'm open to other states as well), are there real estate lawyers specializing in this sort of thing?

Thanks,

John