1. Remember, you can still buy BP's online
2. a 20gallon long tank will be suitable for a full grown adult. A 10gallon will be suitable for a yearling BP
3. A UTH is fine but you must must have some way to control it. A rheostat (or dimmer) is the minimum but if you have the money, invest in a good thermostat.

Welcome to the addiction. You will have a room full of snakes soon enough!