You will need someone that can draw a plan which is acceptable to your building department. The title of the person does not matter (unless required by your building department). There are good and bad architects and designers. You could try talking to two different general contractors to see if they have suggestions. The contractors (if qualified) will also be able to provide more accurate pricing and timelines.

I noticed you used the term casita. Do you live in the southwest?

Hi, Suzanne,

In your case it probably makes the most sense to pick your remodeling contractor and let them guide you regarding the selection of a residential designer or architect based on the job scope and what your municipality requires for permits.

Best wishes for a successful project.