We will sign players but will have to sell. Moshiri can't fund the completion of the stadium never mind breaking FFP for transfers. It is not only wise to sell before we buy, we will not be buying otherwise.
We'll possibly never know the real answer to this question but there is a difference between operational costs and a stadium build. LOR will want invoices paid that run into the hundreds of millions in one go. Bearing in mind the budget for this stadium started at 300 million and will be 700 by the time it is finished. If it was your money you would want to reduce the risks by sharing the costs too.
That's opposed to if say the best player we could possibly sign became available for 20 million then imho the funds would probably found to make that 7 million or whatever down-payment. You can see a big difference between the two.
The reason we won't fully know the answer to this is that even if MSP or another came in and said here is 100 million for the stadium and 50 for players we'd still have to sell players as we have to start balancing the books to make us 1) more sellable due to less debt and give the owners an opportunity to invest in the squad after any takeover or 2) give Moshiri that same chance to invest once the stadium has been finished and our income has increased so perhaps we can sustain a spending spree this time instead of getting Ancelotti, buying him a few decent players and then saying well if you don't get Europe then that's your lot.
Besides we've been stockpiling gash for years so we need a clear out.