Personally, I think you'd have a hard time unless you want to just do compounding - stuff thats not covered by insurance anyway.
The reason is...the "little" stuff (the $10 copay lisinopril) adds up over time - especially when the pts take 4-5 regular medications. Then...from a pts perspective, having to submit receipts, wait for reimbursement, etc...is all a pain. Most depts of insurance require 90 day pay to providers - that is not the case with pts.
Now...with the big stuff - thalidomide (multiple myeloma), Byetta (diabetes), Enbrel (psoriasis & other dx)....now you have medications which an run in the thousands of dollars per month....could be up to several thousands of dollars.....pts need to know if their insurance is going to cover it & if not....how they go about getting it covered - prior auths, paying down deductible, maximal annual amts, etc.... They won't know that before beginning therapy unless you submit for payment. After they've paid you & find the insurance won't pay them a portion back....they'd want to return it & you can't do that. With online adjudication which we have now...we know insurance coverage within minutes & can get the PA process started the day the drug is ordered.
So.....I think your niche would have to be for those drugs which will never be covered by insurance.