Things work differently from state to state and all the firms I work with won't do anything that isn't high-rise commercial/residential unless you're willing to pay 500x the price.
Some tips that can help:
1) Find a structural engineer first and ask for a recommendation
2) Find a general contractor and ask for a recommendation
3) Drive by any development in progress and ask the foreman who the RA on the project is - you may run into a cunt but for the most part they shouldn't have a problem sharing
Here are design firms in Chattanooga:
https://www.surfacearch.com/
https://www.hkarchitects.net/
If you're going with any structure that isn't timber (steel, masonry, prolly not concrete but who knows) - I can help you on the structural side.