Dear Sir
Neem cultivation is a very good idea. Neem tree is one of the trees known for its overall useful properties.
The most common species of neem is Azadirachta indica. neem has all properties such as medicinal, insecticidal, manure, air purifier.
U can star with seeds too but i will suggest u to grow ur own seedling and then transplant them.
In case of landscaping and environmental value i had suggested big plants.
U can raise the seeds brought from a good reputed nursery or some research centre abd plant in a nursery bed and later transplant the seedlings.