I hate to agree with Daniel Levy, but if you borrow £500m to build a new & bigger stadium on a 25 year mortgage, that will add £20.6m per season to your long-term amortised debt.
When Southampton were relegated, even they received £128m from the PL, & they had additional match-day, sponsorship, TV appearance & any prize money added to that figure.
Southampton's turnover in their last PL season was £151m, so hypothetically taking £20.6m per season out of that with more revenue from the bigger stadium, would be perfectly manageable, as they'd have roughly a £33m amortised annual debt ceiling, with any other debt being levied against the owners personally.
This would leave Southampton £118m to cover wages, operating costs & for transfers. If they need a cash injection to compete in the transfer market, so be it. It would have to come from an owner equity injection.
This should be acceptable to everyone, APART FROM the Cartel Clubs, who fear owners like Sheikh Mansour & PIF who they deem as having limitless state funds, & who wouldn't care about huge annual personal losses.
However, this is a whole other discussion altogether, & leads us back to the creation of FFP/PSR. ¯\_(⊙_ʖ⊙)_/¯