This is a very tricky situation. It is important to enlist the services of a lawyer, preferrably one with intellectual property and trademark experience. Go to http://martindale.com to find a firm nearest to you. Once you enlist an attorney, you should decide what kind of rights you want to sell and for what price. I recommend against partnering with the entity looking to rent your property. Partnerships have a way of going sour and presents a problem with collections. I would recommend a strict payment schedule with ratcheted increases each year.
Otherwise design the project yourself and do it alone. You would probably be better off doing it yourself anyway. Websites start at $500 and work up from there. However with a domain you don’t always need to have a hosting account and a website to make money with it. Stay tuned for more information on this.
The last thing I want to say about leasing or renting your domain, is that you need to maintain control over the domain name. Point the ns records to the renter’s web host, or do a forward. You can do free forwarding with domains from http://domaindjinn.com . Most domains cost less than $9 and hosting is cheap too. However, do not transfer rights of the domain or ownership to the domain to the renter. This is a sure way to lose control over your domain.