I will exspand/build, find, farm, decorate, ect. under 150 rupies on the survival server, unless its super huge, then it may cost more, and depending on size it may cost less, plus the first sale is 25% off! I am an very good designer so interior and exterior aren't a problem unless you provide materials! P.S.- If you provide the materials/equipment the price will definitely lower.
For the designer part, I would recommend that you either provide reference pics/warps of your builds. Just so people have something to go on.