**Just my opinion as I have little knowledge of this but is the below about right?**
Although it doesn’t necessarily matter about your profit and loss from year to year I suppose, it’s your total debt that is the issue. Once that spirals (like Portsmouth/Bolton) and your benefactor/directors no longer want to plug the losses, then its administration time.
If you have saleable assets (stadium, training ground, academy etc) then you’ll get a buyer because there’s something concrete to secure your purchase against and take the debt on. This happened with Bolton initially a few years back. Their problem (and Bury’s for that matter) has been that the successive owners who took over have tried to asset strip some parts for whatever reason (inject more cash into the club, pay off loans the new owners used to buy the clubs in the first place or a potential opportunity to make money personally from the club) whilst continuing to make losses. Loans then get called in, creditors want their cash, tax bills go unpaid. Sometimes the process will then repeat itself but in this instance Bolton and Bury have been so poorly managed, sold key assets (Steve Dale has sold the stadium & car park) potential new buyers aren’t as attracted and pull out.
A wiseman once said, if you owe 100m and can’t pay it back, it’s the banks problem. If you owe 5-10m and can’t pay it back it’s your problem.
The people who took over at Bolton & Bury had no money themselves to stem any losses. They weren’t fans, they simply bought he club with loaned money which they aimed to repay by carefully stripping the club of a few assets at a time and hopefully injecting a bit of cash into the playing side to get some success. They’d then sell the club and make some money back (as would their initial backers). Only thing is it is not as simple as that.