When will you really address the housing availability problem?

[Ryel]

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.

It doesn't matter if the content needs a team or not, prior to 3.1 Kingly whiskers on my server were going for 15mil each split by 8 is still a profit that doesn't require a crafter or gatherer. Additionally there are many content buyers who have legitimately made their gil via crafting or gathering, you don't get to just blanket it with "Supplemented by RMT" and ignore it as a viable source of income for those capable. Especially when that income can very well rack up hundreds of millions in gil over time.

Also if you play the odds on treasure maps you more often come out ahead over multiple maps even if you have poor drops due to the selling of crafting mats and the occasional high price items. when 3.0 hit Thav silks were going for 7mil+ on my server and selling consistently we had a map party going and had people drop multiples of them over time which is easily enough to cover the cost of the maps with a healthy profit.

Before Heavensward we had more than a few bluebirds and nutkins drop to cover multiple maps and profit for people.

RNG? Sure but income is income.

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.

Free income is still income whether it's through luck or not, if you only look at income in terms of large gains your wallet isn't going to fill very quickly, and it's not as if I've suggest these as a SOLE source of revenue, the idea is that you are acquiring gil through multiple avenues so that it adds up over time.

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.

Another poster broke down the marketboard bit so i'll skip that.

Spiritbonding was actually a huge money maker for a large number of players in my FC without crafting classes, they actually went out and FOUND other crafters to make the gear for them at near cost of mats and a percentage cut of the materia profits, this was more than enough during the relic boom for players to hit 10 to 20 mil in a few weeks of doing brayflox (hard) casually with bonus gil if they got a Baby Opo-opo to drop since those were selling for 2mil at the time.

Nobody is saying any of this is easy, but it's more than possible for the casual player.