are you looking for info on how to actually do a business start up? Or just looking for general ideas? I currently own a mobile business (not in the medical field) and I'll try to help.
Due to the high level of personal liability your first concern should be protecting your assets. You wouldn't want to get sued and say, lose your house or retirement money. You can make an appointment with a business lawyer for a new business consultation. It would be wise to incorporate IMO. If you are driving yourself to and from your engagements, your state may require you carry commercial drivers insurance. That is a write off.
The second thing is taxes. A self employed person pays roughly a third of their income to Uncle Sam (if they are a US resident). Depending on your business entity, you'll have to figure out when and how to pay yourself. You will also have to keep track of federal witholding, any state and local taxes, and pay estimated quarterly taxes. You will need seperate bank accounts from your personal ones.
Liability insurance is very, very important as I'm sure you can imagine! I have no idea what something like that would cost.
Do you need business start up money? If so, you will need a business plan or the banks won't even talk to you.
The way to start out would be to figure out what your expenses will be exactly, or as close as you can come. Then figure out what you need to charge (don't forget to add 30% for taxes!) and see if the take home is worth the trouble.
Here is a quickie list to help you get started:
commercial auto insurance
vehicle expenses and maintanence
gas (which is climbing higher as I type!)
business phone and cell
Another thing I didn't think about is how will your employer react to you doing your own thing? Will you be able to solicit clientele from them? If you can't solicit, you'll need a marketing plan. Marketing can start anywhere from a few hundred dollars for a newspaper and phone book ad to thousands for a direct mail marketing campaign, or a radio or tv commercial.
You'll need to figure out a service area too. Keep in mind, as gas prices rise you may not want to travel too far from your home or regular job. My mobile business serves a 9 mile radius of my home. Time spent driving is time spent not making money.
Good luck, and if you have any questions please feel free to ask!