From a design standpoint, you have two options. First, you could start out by selling fursuit parts, which don't have to be factored to fit a person. However, it would be smart to contact some fursuit makers abroad to let them know you exist so they buy your printed parts. Second, if you decide to sell fursuits, customers may have to provide exact measurements. Another alternative is to use a tailoring app that customers could their measurements with, but I would have to see if that app is freeware already.