No they don't. The issue with housing isn't the cost, its the availability. There are a finite number of small houses, and on most servers, all of those have already been purchased. Also, the price of just the workshop/stables/garden is significantly less than that of a house.
I feel this idea is wonderful for stables. I don't really get why they haven't done this already? We can already access multiple stables (they already worked out the bugs with multiple stables not generating multiple chocobos and such) and other people can already not feed our chocos in personal ones, so why not do this in a public place too?
For gardens, it would be nice if there was some way to grow stuff, even if just in two-plot gardens or something. Gridania could have an atrium where you can buy space.
But, for workshops, I don't think this idea would work. For workshops, unlocks are tied to the house/workshop, not the FC or player or ship or whatnot. If you're talking about individuals having airships, well, ranks are tied to the FC airship slot, not to the airship itself. You can change all the parts and the ship's rank doesn't change. You can destroy all your ships and your FC's sector unlocks don't change. You can't put workshops in individual houses. It takes a light party of four people to advance a workshop project. If you're thinking that it would still require an FC to craft the ship parts, but individuals could buy those ship parts on the MB and just assemble their own ships to send out, that would still be a bunch of per-character data to suddenly have to store. And, they want airships to be an FC group activity.
If you're thinking that homeless FCs should have the ability to buy an instanced workshop that the whole FC can access, well, at present all unlocks are tied to a house, not to the FC. Right now, if your FC sold their house and bought a new one, their new workshop would not have any of the unlocks they had obtained. They'd have to start from scratch. For the instanced workshop idea to work, they'd have to change how they are doing things pretty significantly. Also, if that FC then buys a house, how do you handle the two workshops? Do they get separate ship slots in each and separate unlocks for each? Are they the same workshop?