A leaseback to a flight school/rental operation just to soak up idle hours is NOT going to be profitable (or even probably a net gain over just letting the plane sit). I've been on both sides (lessor and lessee) of the leaseback. This sort of thing is actually bad for both sides. The school hates it because the owner wants priority. The owner hates it as the school only schedules his plane as a last resort and the amount of money doesn't cover the increased inspections, triple insurance, etc...
If you want to lease for a business, lease for a business. Otherwise it's fraught with perils.
Yep, this is a huge issue with yachts as well, the brokers tell them "You can charter it out and it pays for your use." This is a lie.
It's either your plane, or a business/capital asset you have leased into service management with someone else. If you want it to 'make money' it is no longer your plane to use, unless it happens to be sitting with nothing on the books and you want to take it up real quick to see how it's holding up and what it needs.
You can have one or the other, not both. That said, I have seen a few, (very few), leaseback programs that worked well for both parties, and they had a few things in common. First off, as mentioned above, the plane was a capital asset only and the owner had no emotional attachment to it. As long as wear and tear is within planned levels of depreciation, no worries, it doesn't have to stay 'new looking'. Second, the operator, not owner, was responsible for maintenance. This means the owner only takes around 25%-30%, but they get that off every hour period, they only collect, they never outlay for maintenance and repair below a certain threshold.
Here is the most important factor they all had in common though..., they all had prior, years long, relationships and trusted the FBO because the FBO had earned that trust, and the FBO took proper care of the equipment.