Hi OP, in case you still want to read opinions here's my 2 cents:
It's too late to set up the Garrisons to earn good gold with Treasure Hunters, not only because you get just 1 follower per week but because the setup is REALLY time-consuming at the beginning, most low level follower quests are less than an hour long, so in order to maximize leveling times you will have to log pretty much every hour to every toon garrison to finish missions and re-send followers.. Not to mention the huge amount of gold needed to place and upgrade buildings and the garrison itself.. Only to make profit for like a month or two? Not worth it imo
On the other hand there's 2 easy things you can do that will still net you a nice amount of gold:
Both of them require at least 5 alts, which you probably have since you wanted to make the garrison strat.
1- Run Cataclysm raids on 25H, all of them.. Thats 10k per toon.. So with 5 alts 50k per week.. Not bad at all!
2- Place a level 1 trading post on every garrison and log with every alt every 2/3 days to collect the GR cache, and check the trading post vendor to see the value for the enchanting dust.. When its 4GR per unit buy stacks of 200 till you run out of GR on every toon and sell them on the AH.
The profit on the second strat depends on your server, on mine they usually sell for 450/500g per stack so selling 30 stacks nets me 14k gold give or take
Hope this info is useful and good luck