Also, broaden your market. There probably aren't that many RPGers willing to pay top dollars for maps. But if you can appeal to the general population you are more likely to sell stuff. Maps of real places in a fantasy style might sell better than made up places.
Hand Drawn LOTR style, comic book style, anime or cartoony ISO style maps of university campuses (back of the orientation guide) or shopping districts (flyer or local sign) might sell because they are fun and useful. Even a map for the local school fair showing the location of the stalls might generate a few dollars.
Some businesses might like to have a clever "how to find us" map on their brochure.
As a photographer I always wanted to do artsy, unusual portraits. I got to do some great work...I even got a few $10k commissions, which was great for the ego... But it was bog standard family portraits, corporate head shots and weddings that regularly paid the bills. So what I am saying is that you might do better taking work outside the purist fantasy mapper channel, so you can get paid, build your skills and get to keep doing what you love.