Well you're not the only mamas thinking about this. When I switched to cloth my father and I discussed starting a diaper service.
As far as the water temp being so high, I'd just get a second water heater that is for laundry or diaper service machines only.
You can start with a second washer and dryer (I don't want other people's poo in with my dishtowels...our poo is enough poo, thank you) and that water heater...and if business booms, you get more machines as needed.
Then there are the diapers...advertise at first for washing people's own diapers. Then you can either sell or rent diapers. That might help you ease into it a bit.
Talk to your ped about posting an ad. Also visit your health food stores and ask about advertising there. Also, kooky little coffee shops with ad boards...other places where "crunchy" folks might hang out.
I thought charging every two weeks was probably easiest. I'd also require a credit card number at first (in case of non-payment). Check with your bank about information on automatic transfers into your account.
Don't forget that portions of your utilities and even house will be write-offs. If you already have an accountant, ask about those things.
Offer prefolds and one or two kinds of covers, for simplicity and ease of washing that much stuff. I also like the idea of selling Fuzzi Bunz for nighttime diapers.
I have a great plan in my head. I just don't have the fire under my bum to get to it. WHY was I born in October?!
Ooh. That site captain suggested is a great resource. If you're not in their area, contact them. They'd probably be very helpful.
Edited: Or maybe not. Looks like they're branching out. They might not be as helpful if they want to be a chain, kwim? Dunno...