Be careful. Putting out a shingle can transform something you love into something you loathe. I have countless stories of friends (and one or two of my own) that loved their hobby but hated thier business. Make sure you are willing to invest a lot of time into a successful business. If you plan to make a REAL go of it (as in 'for a living'), then you must maximize output and minimize time and movements.
If you will enter the fine framing market, it is very much in line to purchase or build a framing jig:
An accurate mitering machine (I preferred a table saw and sled):
I also ended up with a miter trimmer for enhanced accuracy (this is an example of one): http://www.grizzly.com/products/Miter-Trimmer/G1690
You will also need a couple of brad or point nailers, an air compressor to run them, and a host of little things, markers and fillers that make building frames fast and ACCURATE. The art world doesn't like open miters, uneven seams and shoddy construction around their prized treasures.
However, if you will be making pallet wood or rustic frames, then it might be acceptable to have a slightly open miter on one corner, or an unfilled nail hole.
My wife had a framing shop for many years. I made most of her frames and she mounted the artwork. I used mostly prefinished frame stock, as milling and finishing raw stock was simply too time consuming. We still have mat and glass cutters, a dry mount vacuum press, and a storage room full of foam core and mat board.
The problem most fine framers have now are the large chain stores (Hobby Lobby, Micheal's, Craft 2000, etc...). They can buy bulk prefinished framing materials by the truckload. We cannot. The wife now only frames for family and friends. She even retired me and goes to Hobby Lobby for custom frames (I'm a grumpy employee).
My advice is to see if you have a sustainable market before you dive in head first. If you are in a place where the big dogs haven't infiltrated yet, you might make a go of it. Otherwise, I would suggest doing it as a nice gift for family and friends. Good luck.