Ok, first a caveat, I'm no expert on this but I did stay at a Holiday Inn Express last night...
Assume there's no buffer in the beginning where you lose value. Your original sale price of a unit today was 245,000.00, so appreciation is -
3% annual over 10 years - 329K
4% - 362K
5% - 399K
6% - 438K
(Personally I go with conservative appreciation numbers and assume a 2 year buffer where it actually depreciates a bit to protect myself and to establish a bottom.)
On the investment, you said 20K in cash flow breaks you even, so I assume your annual carry costs are equal to 20K. If 20K is all you expect to make on average, with appreciation like the above in most cases you will lose money on it.
using -
25% capital gains rate
28% top marginal tax rate
sale commission of 4%
10 year fixed @ 6%
20% down
20K / year income with 3% annual increase
20K / year cost with 3% annual increase
you get -
appreciation - annual return
3% - 1.36%
4% - 2.76%
5% - 4.11%
6% - 5.48%
With anything but the most optimistic appreciation, your return is less than inflation. Also, note that with appreciation of 6% your return is 5.48% - it will cost you money over the 10 years to carry it. That's important. You would not make money until you sold, or you would have to increase your annual revenue somehow, by a good chunk of change, or cut the 20K in costs.
Also I'd add that if your base carry is 20K, your actual carry will be higher because you will have to replace things, repaint, fix / replace broken appliances, etc.. assuming you haven't taken that into account. (I've heard horror stories about trashed condos from quite a few folks around here.)
Assume a carry of say 22K @ 3% appreciation, your return drops into the negative, you loose money overall. Very thin margins!
Of course, there are so many "what ifs" like what if I make more than 20K a year, or what if a hurricane hits and I lose a season, or what if it appreciates at 20%

...
Hope I've helped. I don't want you to think I'm trying to sh*t on your parade or anything, I just dig run run running numbers and like to help out if I can.