Beau,
First, I have to compliment you on a GREAT post. What a great question to ask.
Next, from what you said, it's my belief that you're already on the right track.
Ann Bellamy pretty much shares my view - I have experienced that it's best to pretty much never sell anything, although there are a few properties that after years, just didn't fit the long term plan, so an occasional sale maaaaaaaaaaay be ok.
Next, she said "buy more properties faster." On that, I fundamentally agree, but buying too fast, like eating too fast (both which I'm experienced in) can hurt you.
John Chapman - you asked Ann to elaborate and she hasn't yet, so I'll put in my 3 cents worth:
Here goes:
I started investing in residential property in 1975. Due to the "mentorship" of someone who had more money then, but ultimately failed and became poor, I "churned," bought, sold, traded, oh boy. Lots of activity, but after the downturn of the early 90's, I had lost a lot of property for the SECOND time, and was darn (is it ok to say darn here?) discouraged that I was working my _ _ _ off but not getting anywhere.
Then, I looked at a buddy of mine, same age, same middle class background, but he had simply trudged away on a buy and hold basis.
Now, my buddy has 4 residences. (No, not rentals, we'll get to that - these are NICE houses sitting there empty and furnished in case he wants to go to the beach, the suburb, the desert or downtown San Fran.) Plus, he's got another nice goodie - 35 almost paid for rental houses and a 10 unit.
Needless to say, I'm glad I adopted his program about 18 years ago, and it's been all good since. Not quite as flush as my pal, but no complaints.
Hope that helps. Sorry for the long post, but it's certainly been a LONG road.
Good luck, and my compliments again on a very fine question. No doubt why you're able to pull down 250k a year in whatever you're doing.
Joffrey