Once upon a time, the perfect business that I wanted to put up was a Rehearsal studio for Band groups. I wanted to think that I did have one. I did have one customer but its not really an official business.
I remember I had 1 group rented the equipment on my studio and another rented the equipment outside on a fiesta gig.
Band Rehearsal studio business is different to a recording studio. For a recording studio you would need recording studio equipment available at Musicians Friend while a rehearsal studio, you just need the musical instruments and amplifiers.