Before hiring a local contractor to build your play court, ask plenty of questions and do your research. Tennis court construction is a highly specialized field, so it's important to find a contractor with extensive experience. Kolkmann recommends using someone who is an active member of ASBA, with at least 15% to 20% of annual business devoted to designing and constructing sport surfaces. (ASBA has a searchable database of certified builder members.)
The origins of the 15, 30, and 40 scores are believed to be medieval French. The earliest reference is in a ballad by Charles D'Orleans in 1435 which refers to quarante cinque ("forty-five"), which gave rise to modern 40. In 1522 there is a sentence in Latin "we are winning 30, we are winning 45". The first recorded theories about the origin of 15 were published in 1555 and 1579. However, the origins of this convention remain obscure.