Lots of thrifters dream of finding an original painting worth lots. Very, very slim to find. Awesome if you are one of the very few, though.
You have to have enough knowledge to know what you are looking at - otherwise, you will buy a décor painting produced in a Chinese factory in 2017. Art can be very tricky.
I remember about fifty years ago when a man found a Winslow Homer painting in a junk store in Tulsa OK. The store owner thought the frame was worth more than the painting.