As for me...I have a two-point plan.
First of all, I don't think I'll ever "retire" completely. Even when I'm 90 I see myself closing at least 12 transactions per year from past clients.
I intend to eventually switch to Exit Realty. Probably within the next 3 years. Exit has a built-in retirement program based on 1-tier residuals. It's like having the benefits of being a broker, where you have people under you working and generating you an income, but without the overhead, extra responsibility, or time-consuming issues.
For every agent whom you "sponsor" into an Exit brokerage who then go on to earn $100,000 per year, you earn about $10,000 which comes out of that agents split with Exit. The $10,000 payout is the max anyone can earn from those under them each year and obviously, sponsored agents who only earn $50,000 will translate into a smaller $5,000 returned per year for your recruiting efforts.
I think that this is the MOST promising plan out there. If you can recruit 200 people over 20 years who end up being high performing agents, then you'll end up earning $2M per year! Obviously, it will take a LONG time to put together a bunch of agents who are top-performers, but smaller checks will show up in the interim years. My plan is to take ALL of this second source of income and invest it. Either in real estate or growth funds so that at the end of 20 years, not only will I be earning $2M each and every year, but I'll have built up a sizable nest egg getting to that point too.
Honestly, this is really the only "real" retirement plan that I know of in the world of real estate that doesn't involve "tenants".
For me I figure I'll always work some - just because I love real estate and can't imagine not having my toe in the water - and I'll always want to check out the interesting houses that are listed! I've never given real thought to selling my business though I know it's smart to make a plan. As for a retirement plan I'm counting on my two-family as my nest egg.