I think Mbemba money, Merino money will be available to Rafa. I assume that is what he is saying. He is having to trade to buy. Understandable of course as we don't want to carry excess baggage like Mitro, Mbemba, Colbak, Sels, Lazaar, Saivet. Good chunk of fees and wages tied up there.
I think he's also saying he may have to trade someone like Ritchie to add another winger. I don't think he'd be allowed to have Kenedy, Ritchie, Townsend, Murphy, Atsu for instance (Aarons too if you like). I think he is accepting to get what he sees as an upgrade in Townsend, the wages and fees have to be paid in part by the sale of another front liner. I can't see a problem with that personally otherwise we will just get into deep water again with wages.
It looks like normal football club trading rules. West Ham have bucked the trend somewhat by buying loads of players and then having a firesale. I don't think Ashley would take that kind of risk with us but that's ok. As long as we improve our squad in the eyes of the manager then we are making progress. The only issue is I suspect Fulham and Porto etc are sitting saying "just sit tight, once they buy their selling position weakens". If it comes to that kind of brinkmanship Ashley will just say "use these players Rafa, I can't get a decent deal". I think that is where the fans are a bit miffed as most clubs accept they have to take a bath on players they sell.