I suggest that you go to a local school or college and chat with a teacher. The instructor will be able to ask relevant questions and give you a far better answer than we can. Having said that, my guess is that you should be able to get a good start with reasonable brushes, paints, knives and canvas, etc., for about $200 to $300.I am a person of extreme talent, how much would it cost me to start oil painting?
If you get to an art store on a good day, you can make out pretty well with prices.
You would probably want to start off with ';student grade'; oil paints. They aren't as high quality, though they are often significantly cheaper than better quality paints, and are fine for beginning. I've been painting for the past 4 years and use them still. On sale here, they run about $3 a tube. It would be good to start off with a basic pallatte...the primary colors, white, and black. In fact, it may be good to get a few different types of primary colors. There are various shades of red, yellow, and blue, and each one will produce a different color when mixed with each other. Also, be aware that using black minimally is a good idea...many blacks will leave a color more blue toned than darker, and it isn't the best approach.
As far as brushes, it's good to get a few different types. You can often get sets of different sizes and types for about $10 or so. They usually aren't super high quality, though they will last you for at least a few months if you take care of them well.
Potentially, the most expensive thing could be canvas. You can often get these on sale, which is definately a good thing to look out for. It may be good to start off with the canvas boards (canvas on a piece of cardboard), rather than stretched canvas (canvas stretched over a wooden frame). It's a bit cheaper, and they have the same surface to work on. Canvas boards often come in packs of 2 or 3 as well, which can also save you money. If you do want the effect of stretched canvas, you can glue wood to the back of the canvas boards. It works just as well.
If you know where to look and are careful to look out for sales, you can start off pretty cheaply.
Start out with a basic set of oil paint....then add a few more tubes of different colors that you really like. Buy about 5 good brushes,a few canvasses, palette and cleaners. You could probably start out by spending around $150 to $200. If you can sell a couple of paintings then use that money to buy some good painting supplies. There...you are all set.
a little humility