When will you really address the housing availability problem?

[Colorful]

Ex primal mats - Required a team.
Coil mats - Required a team.
Treasure maps - Need a gather to get the maps unless you're spending money to buy them which in some cases you would just lose more money than you got.
Content sales - Usually supplemented by RMTs also required a team.
Daily/Weekly challenges - That's not a lot gil and especially not enough for the millions you need.
Retainer Ventures - You'd have to get super freaking lucky to consistently find mats that would get you the millions you need instead of the standard fish they bring back.
Playing the marketboard - Maybe, but without a good supply I can't see how you can play the marketboard without your own injections.
Spiritbonding / Materia sales - You'd have to keep buying the gear to spiritbond with and hope that the money you spent on the gear was less than the materia you got.

I took out the others because they didn't exist prior to our current problem so I can't comment on them today. These were the only way to get money before Heavensward when all the houses became sold out.

What's your point with content requiring a team? Did you post not state any method with a crafter or gatherer class? But it does depend on the house size, for a small, unless you're the most unbelievably lazy player there is, 6 million gil in easy to make, even without crafters or gatherers. I've made just about 1.6 million through Diadem since release, and I do it maybe once or twice every 2-3 days and sell the mats. Now, I've heard on other servers the mats go for 100k-200k+ while on Tonberry it's a rather small 30-70k, so if you're on another server you could double, or even triple that number. Near the release of Heavensward I farmed the dragon materials, dragon skins, dragon blood, etc. In an hour I was making 150+ depending on how much RNG decided to love/hate me.

If you did it casually, you could easily afford the money to buy a small house, no questions asked. Now a medium+? Well, unless you have a raid group selling clears or are a very dedicated grinder, it's going to be tough.

Edit: looks like I forgot to read your last point, but toadskins are still a viable beginner way to make gil, and I'd have to assume that pre-HW they were far more valuable along with other materials.