Mod The Sims - A House on Stilts

Placing this lot in your world
With a few edits, this lot can be placed in any world in any appropriate place. It is important that you find a good spot before you place the lot. You want to find a place where a road is placed next to a hill that isn't TOO steep, but still goes down up to 2 stories in the back. Using the World Editor button in Edit Town, place a 30x30 lot or use an existing lot with this criteria. Place my lot.
When you first place the lot, it should look like this:

This is normal.
Next is the harder part. You will need a cheat for this. Open up the cheat console by pressing Ctrl+Shift+C, and type in the following cheat:

constrainFloorElevation false

Afterwards, enter build mode on the lot and use the landscaping transformation tools to contour the lot to your location.
IMPORTANT!
DO NOT change the elevation of the top and bottom of the stairs in the front of the lot. This will make them unusable! If you need to, save a reference point on the terrain by taking the level terrain tool and dragging it to another area.

Some tips to getting this done is to raise or lower the terrain to where you need it to be to match the edges, and then use the soften tool to make the lot blend with it's surroundings.
Don't be afraid to transform the elevation underneath the house, but leave at least 1 square the same.

It should look like this:

Cleanup
There a few things you will notice after making proper terrain modifications. First of all, you will notice that the poles are snapped back to their original places, and that the house's floor is completely distored. There is an easy way to fix all these problems.
The Poles:
Simply take the hammer (delete) tool and hold+drag from one of the corner poles and delete EVERY pole. It's also okay to delete plants or other things. Hit undo or press CTRL+Z and they will snap back to their proper positions.

The House:
This is quite simple as well. Head over to the terrain tools and find the Level Terrain tool. Find a spot on the floor of the house that is not affected. (If you do not have a spot like this, it is very hard to recreate the perfect elevation. I would undo until there is a spot that is perfect and do the following directions first, then fix the terrain) Use the one spot to level the rest of the house by clicking it and dragging to all corners of the floor (including the deck). This will fix the second floor automatically. You're about done!

The final step is terrain painting and planting. As a base, I would erase all the terrain paint that is on the lot to match up to the world, and then paint over what you feel you need. Add/Remove plants as you wish! Enjoy!

Further information about placing/replacing poles