Donny is correct about it being a money pit, and the chances of your ever 'generating income' from it are about 1000/1. The reason is because 98% of musicians already have some kind of home recording capability and the ones that want a quality level above that want a PROFESSIONAL studio way beyond what can be provided in a converted den. They would also want professional level engineering/producer services which you probably can not provide.

Depending on the gear you already have, a home studio for recording your own stuff can range from $500-2000. A 'pro' studio (drum room, acoustic treatment, 'pro' mic drawer, etc.) would probably start at 10-15k and go up to the value of your house (and beyond). The MOST difficult part though, is mastering all the skills necessary to provide professional quality recordings. I hate to sound so negative but, like riding motorcycles on into old age, some things sould a lot better in our imagination than they do in reality. JMO, though. YMMV.

chas