second story addition or not?

hello.
great treads, So, here's what i have, I just bought a small 1300sq ft house with an extra 420 tacked on to the back of it This addition in on a concrete slab, which is different from the rest of the house which is raised. The slab isn't just a patio slab. it is thick with at least 2 feet of perimeter footing where is looked.
The addition is 28 X 15.

here's what we want to do:
1. raise the floor to the level of the rest of the house (bringing slab-level up to main house floor level about 2 feet)
2. then we want to remove the exiting ceiling which is the correct height where it touches the main house, but too low once it slopes down (about 12 degrees).
3, From there we want to build a second story addition that mirrors the previous addition (28 X 15). This upper space will be a master BR and bath.

My worries are at least two-fold:
Can my existing slab take this kind of weight? If not, is there any way to salvage it without rebuilding th entire structure? can it be reinforced?

Also, given recent discussions of cost, what would something like this run me? not including the bathroom and bedroom details. Any sense? basically just to frame it all

For those who want the longer picture, basically we're deciding if we should just raise the floor as it is (bringing it in line with the rests of the house) and add a new roof (at bottom it will have to be raise at least 2 feet)

which one sees to make more sense? we are on a tight budget, but as my dad used to say, my wife recently swallowed a watermelon seed, so in 9 short month we'll have a watermelon that looks a lot like baby....and an extra room would be a big help.

Any help or tips would be most appreciate.....we are also redoing the kitchen right now....straightforward, but expensive.

THanks so much, any thoughts..??.. mark elmore *********

 

I'm no architect and have no way to determine your situation. But I has an idea to save money. Lift the addition eight feet and build a first floor. You need to judge the feasibility.