House Flipper

For this achievement you have to sell a house to Chang Choi

For me this proved to be the most difficult "specific buyer" achievement in the game, but doing the following netted me the achievement (on two different accounts to ensure it's repeatable)

First off, buy the home Abandoned House

Take out your hammer and knock through most of the walls to turn the house into one 39m squared space

Add the following items EXACTLY

1 x Bookcase Kall
1 x Single Mantis Bed
1 x Standard Desk (Make sure this is next to the bed as it's one of his criteria)
1 x Swivel Chair
3 x Teddy Bear
4 x Ball
4 x Bunny
4 x Little Bunny

After this, install a Sink, Toilet and Bath / Shower (I personally went with bath)
Fit radiators if you like, just to get a little extra when selling.

Screenshot:

Sell a house to Chang Choi to unlock this achievement.
To get him as your buyer with minimum effort:

1. Buy the hacker loft.
2. Do not clean or tidy anything, go straight upstairs.
3. Sell the bedside table on the left of the bed.
4. Tidy just enough of the mess left of the bed in order to fit in a desk.
5. Buy and place a 'standard desk' as close as you can next to the bed.

Chang should now be your buyer. At a loss (around - €7500), but achievement unlocked.
If desired, you can negotiate in order to sell the house with a profit instead.
I tested this solution 6 times and each time I sold to Chang Choi with €0-€100 total profit (ie, negligible but not a loss).

This 100 GS was EZPZ for me.

If you want to do what I did, choose the Hacker Loft. After cleaning the place up, I made no changes to existing walls.

I used the same furniture as Saikred in their guide: the Mantis Bed, Bookcase Kall, Standard Desk, and Swivel Chair. I put them upstairs where the old bedroom previously was.

I redid all the walls green. I used a mixture of paint and tile. Paint for the living area and tile for the bathroom and laundry area. I went with beige carpet for the living area and light yellow tile for bathroom and laundry, because my eyes like green and beige and the light yellow goes with beige well. Paint was Pistachio Green. Tiles were dark green tile for the bathroom, and 2 Shades of Green for the laundry room/hall.

You don't have to use the exact paint/tile I did. This buyer just wants green walls.

Sink, shower, and toilet in the bathroom. I like the standard Mountable Shower, Toilet Flatty, and I think I used one a mountable sinks with stylish cabinet. I forgot which one though.

The biggest challenge with the main living space is the lighting. I wound up using all types of lights: ceiling lights, standing lights, and wall lights.

The front area I flipped into a laundry room/entry hall. I put a washer/dryer and garage shelf on one side and a bunch of corridor furniture to store shoes and coats on the other side.

I flipped the living area into a dining area for more lighting and I spruced up the kitchen area. Not sure he cares about the kitchen, but I like building kitchens for some reason.

I replaced all the doors with glass doors because I am apparently on a glass door kick right now. Sold for 9,000 euro profit.