It's not just about the owners, there's still the equivalant rules for financial fair play down there. You can have the richest owners in the world and not be allowed to spend it if you have no fan base or sponsorships unless you're willing to cook the books. I don't know what the intention ever was with Salford, but their tiny fanbase is why they were always going to find it difficult to continue progression.
For League One and League Two there's SCMP, for Championship it becomes PSR. SCMP focuses on wage to turnover ratio, 55% maximum in League Two, 60% in League One. Championship focuses more on total losses allowed, you can go lose upto £41.5m over a rolling 3 year period currently.
Right now I'd say they're in a good position vs many League One clubs. The 13,000 attendance they got yesterday will be one of the top 4 or 5 in the division if sustained over the season and they have big outside sponsorships due to the interest in them from the documentary/who the owners are, appearance fees from the summer tour and whatever they're getting paid for the documentary itself. They must be one of the clubs with the best financial position in their division, perhaps the best of all. It's only Birmingham or Bolton who could feasibly rival them for turnover I think due to their big crowds and Wrexham may well surpass those two due to the unique outside income they receive.
Who knows how long the buzz will keep up? TV audiences can be fickle, and people lose interest in things for no rhyme or reason sometimes. If they got stuck in League One for a while then that could hault momentum if people were to stop watching the documentary or if it got cancelled. If a club reaches the Championship then the owners can dig into their own pockets to much larger extent if they want, but then they're facing other clubs whose owners can do the same and run at a bigger loss if they want to as well. More of those clubs will have much larger stadiums and/or a bigger traditional core fanbase plus then you're facing clubs with parachute payments having been in the PL too.