The answer is maybe.
If the current owner has a mortgage, the lender will not allow it. They don't want to subdivide their collateral.
Selling a percentage of the property is possible. This is done all the time by co-owners.
Selling rights/access can also be done. Some people use a variation of this to get solar panels on their roof. In some cities this is even done to allow a property owner to sell roof space to another entity to put a green roof on the property. The other entity needs to counter balance the loss of non-impervious surface on another property.
If the right are done to allow the other person to add a structure to the property, then local zoning laws have to be researched. The property must be able to house that new structure. Their may be limits on height, square footage, number of kitchens...
In the United States a community association might also have to be part of the approval process.
A lawyer will have to get involved to make sure that the addition of the new structure doesn't jeopardize the integrity and legality of the original structure. This will haveto be done at the start of the process.
Selling the property in the future will be complex, and will have to be addressed. If you sell what happens to the other owner. You may have agreed that the new owner can do X, but what if they sell to somebody else who wants to do Y.
There is no standard form to do this. Expect that this is not trivial.