Hi Phil, I am a licensed agent in NY State and work with a boutique agency by Union Square. As an agent you are an independent contractor and you choose how you run your real estate sales agent business. You can focus on rentals or sales or both. Residential or Commercial. You can do it part-time or full time. Like myself, I'm an investor and a real estate agent. I like working with investors because I can identify with them easier.
You don't need to tell a sponsoring broker that you don't plan on becoming a power agent. If you close a few real estate deals as an agent they get their investment back in you. Just choose your sponsoring broker wisely and watch out for the ones where they charge you a monthly fee. You should also ask if the broker owns investment properties. If they do that's good.
A NY real estate salesperson license is only good for NY. The only benefit I see if you're investing outside of NY and you're dealing with an agent there, you can probably get better cooperation. Professional courtesy.
Lastly, you need to be sponsored by a broker in order to start practicing.