OBD2 fault code readers are readily available, just try a Google search. I have a bluetooth one purchased from Vital Engineering and it has paid for itself several time over as some of my modifications cause the MIL to come on frequently.
Its worth noting that with these you will only be able to read fault codes and reset the engine warning light, most of those that work on a PDA or computer can also display live sensor data if you have the software, which is available as 'freeware'.
You cannot alter any engine or alarm ECU settings with OBD2 readers, for this you still need a Testbook.
OBD2 fault codes are also quite general, and not as specific as a manufacturers code (which you need the manufacturers equipment to read) so diagnosing fault wont be quite as easy.