For Inferno capes yes because there is only few peoples who sell them atm. But in the same time, it's really hard to do them without getting banned/cape removed and you need to be trusted to sell an such service because one infernal cape costs like few hundred dollars.
I don't know about fcapes, there seem to be lot of competition.
Infernal capes their still cracking down, also most people aren't going to trust someone with $500 bucks on pixels. Because most people can't afford ely's and stuff so its really time consuming to do it in welfare.
Fire-capes tons of services here, so unless you can beat their price, probably not. Not to mention they have time in this forum.
Infernos yes, but like everyone said, would be hard to find the trust. Fire capes would only be worth if again, you had trust and could get multiple at same time, maximizing profits. Maybe 1 pray fcapes?