Woodrow, all three of my 92107 properties came by watching the market almost daily and swooping down like a hawk when a well priced one came down.
The good thing for you is that your townhouse probably appreciated more than the SFH you want to trade it for.
If you can marginally afford it, buy and rent the SFH now and live in the townhouse.
I still have not moved into my biggest OB home, the rent is just too good on it. It is hard when I inspect or repair it and see how nice and big it is, to own but not enjoy it.
