I say go with what attracts you the most in your price range. Don't just buy a morph strictly to breed it to make money.
Though buying several normal females and a male spider, pastel, or mojave (or as many as them as you can) would be a good start...From your first batch of offspring...keep a female to breed back to your normal male..as a way to increase the gene pool.
Unfortunately I really don't know the prices of morphs in the US compared to what they are here without researching...not sure how much baby lesser platinums go, or ghosts, etc... Pastel males are probably $200 or less in the US..same with spiders and mojaves...female babies, if you go for say, the captive hatched..you could get quite a few. Then you can breed them all to the co-dom and dom males (either one or two females per male, or just breed all the females with all the males, thus getting mixed parentage in the clutch).
Check the classifieds here at kingsnake and various big ball python breeders..see how much typical specimens of each morph costs, then look at what combination they can go into...decide what sort of end result you want to work with, or what morphs specifically you want to work with.
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PHLdyPayne