Patty -
No taxable gain, because you sold it for less than your cost (net of depreciation).
As for a taxable loss, the answer isn't clear.
Once you start renting, your tax cost for purposes of depreciation and for purposes of determining a possible loss on sale is the fair market value in the resale market (your sales market) at the date you converted from personal use to rental use.
So let's say the value was $20,000 on that date. Over three years you were entitled to - and should have claimed - about $2,200 in depreciation, reducing your tax cost for loss purposes to about $17,800. (That's the result whether or not you actually claimed the depreciation on your tax returns.)
Since your selling price ($20,000) exceeds the tax cost for loss purposes ($17,800), you had no taxable loss.
The depreciation, maintenance fees advertising and other rental expenses should have been reported in each of the three years on Schedule E of your tax return, partially or fully offsetting your rental income.
For the rules on how to treat rental income from a timeshare for tax purposes, see post #4 in
this thread.