You seem to have a very optimistic view of tower cost / rental.
For a good laugh talk to the ham radio guys about what a decent 150 foot tower would cost in total, not just the tower but the installation, base, guying, etc.
Now don't get fooled by people who don't know what they're doin... all that "a section of Rohn45G is $300 delivered, so 15 of em is only $4500 ... well you're forgetting that 45G is "ham grade" and can only self support to 40 feet or so... You want something 150 foot rated (and here we need icing high wind rated not that "60 mph no ice" BS that some towers are advertised at). On the good side I assure you a decent installed tower will always be cheaper than a similar height mini-skyscraper, so figure a small 15 story building would be a couple million bucks installed, I assure you a 150 foot tower will be substantially less.
Its interesting in ham radio how the "1500 watt limit" has gotten much closer to affordable over the generations but the "less than 200 feet AGL and the FAA doesn't (usually) care" limit is just as unaffordable today as it was when I was a kid.
As for rental vs buying, realize you've now got two middlemen who want to make a fat profit, the tower operator AND the bank who made the loan. On the other hand the financial advantages of sharing the cost are huge, so pretty much either you're renting to someone or you're renting from someone else.
Also unless you're in supersprawl forget a municipality demanding free wifi for a tower permit. All our city public service is on the county trunk system and via the luck of the draw there are no county system trunk towers in my city (about 4 surrounding it, sure...) so you can't force public access for a city as a permit issue or you'll just end up in another city or having to force county wide public access etc. Of course out east some counties (and some states) are smaller than our cities making it even more complicated.