For newer magazines, my advice is to pull the Arnold issues, movie star issues, swimsuit issues, and any with single fitness girls on them, and then sell the rest in bulk lots, eg - 4 Flex magazines from 1996, etc..... People still pay ok for single issues like the ones listed above, but it's hard to get rid of other mags from the 90's - .
Shipping kills a lot of the profits, and it usually takes a long time to sell anything but bulk lots. There are guys that make $10 - 15 an issue, but they might have it up on Ebay for a year or two before it sells.