That's a good question, "How does one even begin with paintings?". I'm currently looking at that including Watercolor Paintings and expanding that into a lot of other areas including Limited Edition Etchings and other types of Prints. Often I see some nice work in all areas at great prices so I don't just don't want to limit myself to paintings but that is my preference. I'm also limiting myself to $25 for any piece of art work. I don't think I can get burned that way. Since I just started looking into this I don't have any resell stories of my own to tell although I wouldn't mind hearing someone else. I heard of where a guy in Texas limited himself to $35 for paintings that he would buy at yard sales, flea markets, etc... and he's now a millionaire because of his purchases (the story went something like that).
I would almost never buy any of these art works unless I liked it and would consider placing it on my wall. I say "almost never" because there is also a lot of value in the frames, glass, matting, backing and other hardware that you can get with a very cheap bad piece of art at a very good price and even re-frame a great piece of art work with it. Here's an example, I have this really nice Watercolor that someone did for me. To get what I consider a nice frame including everything and framing it myself might cost at least $50 or more (it can go much higher). I've been looking for a second hand frame for a couple of weeks now while I look for other things and found a nice one for $8 with an original Oil painting in it that I wasn't too crazy about. I removed the old oil painting from the frame and re-framed my Watercolor with it and it looks fantastic! I guess that's the other consideration. Even a nice piece of art work you buy might look a lot better in a nicer frame for reselling so you may end up looking for artwork and frames at the same time if you already have another art work to re-frame unless you want to buy a new frame which might cut into your profit margin.
I would agree that research is the most work and can be overwhelming even if you know in advance or after you have purchased an artwork. In the case of going to a yard sale or thrift store, flea market, etc... there's really no or little time for research, you could carry your hand held device with you and do some quick network searches on the artist name to see if you've stumbled upon something. But then that is where luck may have to come in play and some experience with identifying a reproduction oil painting, watercolor, etching, artists or anything else. You may also want to consider bringing a small magnifying glass with you, even better if it has a light attached to it so you can look at the fine detail of the work to see if there's dots in the print or if there's paint over print to help you authentic if it's real or not.
What I would do is ease into buying paintings and stay away from any type of pressure sales like auctions unless you really want, like, and know about that piece of artwork and its value. I would also start out small and set a maximum dollar price you are willing to buy any artwork for or a weekly or monthly allowance set aside just for that purpose. Also, use that artwork as a basis to test the resell market for the artwork you have bought. You may want to narrow the art theme field and buy only artwork with Indians or Cowboys or both in them. Or perhaps art with just Ships or certain types of Animals or made just by certain artist. That way you may become more knowledgeable about certain themes or artist of artwork that are more in demand at this given point in time. Yesterday I bought a Limited Edition framed print by a well known artist of a Lab Puppy in mint condition for $3. I looked up the estimated value on it and it was between $225 and $275. I don't think it's worth more than around $100 and that's only if someone is willing to pay that amount for it. It may be hard to turn that around fast and I may have to sit on it awhile and even drop the price before I sell it. So the next question would be just where to start your asking price for the artwork you have bought. Other things to consider may be finding someone who can restore a nice piece if it's worth doing it.
There are a lot of things to lookout for and it's almost a gamble a lot of time. You will probably see a lot of artwork from these starving artist sales and artwork boiler houses and reproduction shops. It's out there and there is a lot of it. There's also a lot of competition out there, almost like the people who frequent those storage auctions (that's another place to find artwork but risky again). I've been in thrift stores before and seen lots of well dressed middle aged men rifling through the artwork at lunch time and after normal work hours. I've seen when the cart loaded with restock artwork comes out and all the people in the store swarm around and start grabbing the artwork before it hits the shelf. I've seen someone pick up a piece of artwork that someone else wanted but didn't get it first so they kept following them around the store to see if they would decide not to buy it and put it down. I think this Antique Roadshow is starting to send people into some kind of frenzy.
Kevin