My Mum's local Post Office was saved, (not a countryside one). But whenever I go in for Mum's Pension, it is deserted and the postmaster looks bored stiff!
The shop part is very sparsely stocked because no-one buys anything there! They sell cards, but not many.
You need someone to check out the turnover and profit very carefully for you. Also several have been robbed in this part of the world, so I would be too frightened to take one on.