Re: Medium Wealth residents

To get medium or high wealth residential (or commercial), you need to plop a few parks of that wealth next to the green (or blue) zone. There are buttons along the bottom of the parks that show which wealth level they are. The $$ give medium wealth, the $$$ gives high wealth. Certain city buildings will raise wealth classes as well. Check the land value map (F7 or icon on the right side of the parks menu) to see the land value area.

If you change the wealth level of existing residents, they will not change automatically. The poor sims are still living there, until it gets too expensive for them and they move out. To get medium wealth residents right away, you should either zone a new area with $$ land value and let them build there, or demolish the poor sims' buildings so the wealthy can come in and gentrify the neighborhood 🙂

The easy part is getting the medium wealth residents; the hard part is keeping them happy.  Higher wealth classes are picky about where they live. The high wealth is even worse. You need to supply some commercial for them to shop, they are more affected by crime, fire, education and pollution. So the game will start telling you that you need medium wealth residents almost right away. It doesn't mean you have to place them. If you don't have enough simoleans to plop down a fire station, police station and clinic, you don't have to lure in the hoity-toity right away. And remember - education is your friend. If you have a lot of fires and high crime rate, you probably need more education. 

Have fun!

edit: A good rule of thumb is to zone each wealth class approximately 3:1:1 RCI (one commercial and one industrial building for every 3 residential buildings) Put your commercial interspersed among the residential, and put the industrial downwind from both. That is an approximate ratio to keep sims happy and the game fairly balanced.