The Sancho deal doesn't kick in until the summer unless Chelsea trigger it this month with is highly unlikely.
Selling Zirkzee, Antony and Casemiro this month will only put their transfer fees into the current debt.
The ONLY way they can make money this month so they can spend is selling Rashford as it's pure profit however it looks like no one is interested in a permanent move due to his high wages and piss poor attitude. There's absolutely zero chance he goes to Napoli. I would say PSG on loan but that doesn't help them.
Don't believe what the media says. They are dangerously close to PSR and FFP limits. Unless they sell academy trained players they can't spend this month