IMO it would be a very difficult business model or even a disaster-waiting one. Here are the scenarios I can think of:
Assuming you got a very qualified person with all the knowledge's about tax sale in the areas.
How are you going to compensate his works ?
* By the numbers of the purchases ? the more he buys the more he makes, so he is going to buy EVERYTHING including junks, landlocked, burned down, worthless ....
* By the percentage of the winning bid purchases ? Same reason as above, he is going to be the top bidder without any considerations.
Where is the purchase fund coming from ?
* Yours: can you trust someone with tens or even hundreds of thousands dollars to represent you to make purchase ?
* His: if he gets lucky and hits a very good bid, what make him send the purchase your way ?
However, you can get on the "remote tax sale" purchases is to "2nd hand purchase" (buy from bid winners) . Of course, the purchase price would be bigger than the wining bid to convince the seller.