Cpt.Iwillbe, according to unverified sources, the cheapest hour building is in Argentina and Uruguay, but you may get bitten on the cost of travel to and from the place of training...
In fact, the cheapest hour building is probably to pool your money together with 3-4 other hourbuilders, buy an old two-seater and share it. It will be cheaper than renting even if you throw the plane away after you are all done; if you can sell it, it will be still nicer. Of course, the real trick is to manage all that, which may require one of the owners to be a seasoned pro.