Advice on floor construction during remodeling

[villavägen]

Hello
I have a garage from '59 with an uninsulated slab that I plan to convert into a bedroom, laundry room, and sauna.
What is the easiest/cheapest way to insulate and heat the floor?
I've looked a bit at joists on supports, that alone would cost 20k and then insulation and floor chipboard need to be added.
Are there other alternatives?
I'm happy to receive suggestions
L-G

 

[GoForIt]

Hello!
There are different spaces, bedroom versus laundry room/sauna.
Is there a floor drain there today? Are you considering a shower as well?
Is the slab on grade above ground?
Any moisture problems today?