@Jeff Cliff for a good amount of residential work in the US you are generally not required to have an architect, this varies by jurisdiction so you will just want to check with your local building department to confirm. If you are doing any structural work the jurisdiction may require stamped structural drawings and calcs for seismic.
Since, if I'm understanding correctly, you are planning on holding the property, doing minimal work now to get the place rent ready, and then rehabbing it to its full potential for your retirement, it might make sense to have an architect weigh in if for no other reason than to plan for the future home. This will help to ensure that you don't do work for the rental that will get in the way of the future work. If you have no idea what direction you want to go then and some rework isn't of concern then you can likely get a good contractor to get the "done for now" part completed.
During the interviews I would ask to see examples of their work, try to get an idea of how they price their services and what it would take to get a bid, if they see any areas of concern that stand out to them, and check to see if they will be handling entitlements for the work. I'd also ask about their schedules. If they are an investor or have experience working with rental housing that's a bonus as they will know what their target is in the design / build.
Painting with a broad brush here so feel free to reach out with any other questions.
Best,