When is it time to sell?

[Nolan Marshall Jr]

So I've owned a few properties now for several years - oldest 24, newest 5.  A great time to exit was last year, but didn't pull the trigger for tax reasons - high priced 1031 exchange didn't seem like a great time.  And I missed the opportunity to mortgage everything to the hilt and go shopping this year.  Ugh.

2 questions: 

1) Are there some heuristics for what ROE (return on equity) and expected appreciation indicates a sell position v. a hold?  From the news I'm seeing, it looks like prices will be flattish for a period, with some additional downside risk if the fed pushes rates into the 8% zone.  Of course, that also creates owner financing opportunities.

2) Any good posts or info on ownering financing?  Pluses and minuses?  Have found info online, but stories area always welcome.