Sorry to dash your ambitions, but buying such a small type in the US makes no economic sense, by the time you add the costs of ferrying VAT etc, it would be chaeper to buy one here. Second, it is very doubtful that you could actually fly a 150 accross the Atlantic, you would have to fit a huge ferry tank and would have no load left for the pilot/pax. You would need to ship it in a container so therefore, now add the cost of dismantling and rebuilding when you get it back. These things alone will eat up most of your $20K
Third, who is going to fly it back? You wouldnt get insurance unless you have prior experience and would not be qualified without an IR, so that means paying a ferry pilot - eating further into your budget.
There are other ways to go hour building.
Fltcom