Building flying buildings

So, whats the score with flying buildings? do I need to buy land to be able to use the airspace above it, can I rent it? or will most people not mind as long as I'm high enough? I'm asking as I'm looking at this for a project and I don't want to step on anyone's toes.

you have to have your own land, rented or bought.

If you build on someones land, it will go from their prims and mostly they don't like it.

better rent or buy land for yourself

People absolutely will mind, and will most likely return your prims and Abuse Report you, if you build in the air over their land without permission. So yes, you need to buy land, and keep your build within your property lines.

Some individuals may, if asked politely, allow you to put something modest on or over their land. I have two close friends whose housing needs in SL are very modest, and I allowed them to build a little sky house over my land. They are essentially long-term houseguests on my property.

But every prim you use over someone else's land is a resource they are paying real money for, each and every month. So building a home over someone else's land, even with permission, is like camping on the roof of their RL house and running extension cords down to their house to power your electric gadgets. They pay the rent/mortgage and the power bill, and you just use what they pay for? Not very acceptable, in most long-term circumstances, unless it is a very good friend.

depending on size, prim amount, type of project(build) and duration, i *might* be willing to sponsor

this would be on an island and in the sky and depending on size, an pre arranged building location to stay within