I've run several of my own businesses during and since college--
1) freelance writer/editor (still do this now and then when the mood strikes)
2) freelance graphic design and marketing--did that for around 15 years
3) custom needlework and quilting restoration--way too much like a job!
4) designed personalized miniature Christmas trees (did that for three seasons--now I only do them as gifts for friends!)
5) sold dog obedience supplies and breed specialty items for 20 years (started by managing a local dog obedience club's inventory; ended up buying them out, providing their class inventory, and doing limited retail sales as a dog show vendor to support showing my dogs, my other 'habit')
6) dog trainer (kennel manager/groomer, curriculum development for hire, class instructor and private trainer specializing in 'difficult' dogs) -- still consult on a difficult dog now and then, but no longer actively teach either classes or private lessons except on a one-time professional referral basis)
Loved the freedom and the hours and (most of the time) the work.
Hated the hours, NY state paperwork and the cash flow issues of maintaining a retail inventory.
Loved the hours, freedom and challenge of training and writing about training for a living.
Hated the hours, and presenting the reality of life to humaniacs who were/are absolutely positive that 'there are no bad dogs' (or cats, or birds, etc.).
Most of all, hated trying to restore a 100-y.o. victorian while doing these things, and being told that I made too much money to qualify for the renovation assistance development area loans that were happily handed over to other people in my neighborhood who were working at more conventional jobs!
20 years ago, to help with cash flow, I took a temporary position as an animal tech in pharmaceutical research with one of those billion-dollar corporations everyone loves to hate (until they get cancer, heart disease or diabetes, that is...) The day job pays the bills, gives me unlimited access to office supplies, allowed me the financial fredom to take courses toward my masters and towards a couple of techie certification, and provides me with reasonably comprehensive health insurance which became pretty important a couple of years ago. I get paid for technical writing and editing, training and software acceptance testing.
I love my work, but my condo (sold the victorian!) will be paid off in a year and the truck is mine free and clear with only 60K miles on it. Aside from a continuing need for affordable health insurance, I'd quit tomorrow. I can shift pretty easily from writing and editing for hire to freelancing, and I've learned over the years that I can make enough money to live doing just about anything. There's a growing market for software acceptance testing consultants who understand GLPs and the relevant federal regulations, and can successfully guide a team through that process.
Or I could always go back to training dogs for hire...which despite the risks was always the most satisfying part of my day.
