We have been purchasers this way - two times... no problems -
we tried to sell one house ourselves... a two family last year... and we just slapped a sign on the lawn...
got LOTS of calls (half from realtors asking if they could list it)
One "serious Buyer"
gave a 2k deposit, had a Prequalification letter from the bank, signed a P&S
Had our tenants move out (and they were friends actually had them move into another apartment we had empty and into a friends)
Then they decided they didn't want to pay what the bank wanted
so they put a stop payment on the check
and we were left with a two family empty in the fall in MA (bot good insurance wise, heating wise, etc) so we listed it with a realtor who had it under agreement in two days. (with an aquiantence of ours who didn't know we were selling!)