Only vendors I've ever had that made any money were horribly under-priced vendors (I sold decent-good-high end stuff) or Bags of Sending/Powder of Trans vendors. The Recall vendor I had was pretty decent also.

I tried the resources out (leather) but couldn't keep up with the demand, so it is viable if you have the gametime to keep up.

Being a merchant takes too much vested time IMO, but that's because I like killing. A successful merchant has to spend the time comparing prices/keeping stocked/knowing demand/keeping customers/attracting new ones.

agree with Dip, I like to kill not spend hours trying to stock my vendors, shoot, I have vendors at Kits and I havent' check them in a week,

It can be easier to rent a vendor spot from an established shop - then at least you don't have to worry about advertising and all that.