First of all, you probably want to consult an accountant, also the 27.5 is a rough number - but there are actually IRS tables you should reference to get the exact amount.
Depreciation - the initial $25,000. You need to first figure out what the land value is vs. improvements value. Look up your property on the local tax records database for assessment values. In 2012, lets say that when you purchased it it was assessed at $32,000, $5,000 for land, $27,000 for the building. You would take the $27,000 / $32,000 = .84375 (ratio of improvements to total value), then .84375 x $25,000 (purchase price) to get a depreciate basis of $21,093.75. The $21,093.75 would be what you divide by 27.5 to get your annual depreciation amount, ie: $767.04 annually or $63.92 a month. You can never depreciate the land, only improvements.
Using your numbers, the $22,273 is just the adjusted basis - so you basically have a gain of the $2,727 since you sold it for greater than purchase price.
Most people explain that depreciation is an awesome tax benefit. I feel like I got shafted on my taxes for 2012. I was charging $700/ month for rent, paying $500/ month for the loan, and $100/ month for insurance and property taxes. I put $100/ month in my pocket and handed out the other $600, but was taxed on $700/ month income. I got deductions for property taxes, insurance, and interest paid as well as 1/12th of the $909 depreciation. All told, I profited $100/ month, and owed taxes on approximately $400/ month. I paid more in taxes that I made. How is this a good thing for taxes in the short term?
Your numbers (in a nutshell)
cash flow:
Revenue: $700
Mortgage: ($500)
Insurance & Taxes: ($100)
Cash Flow: $100.00
net income (taxable)
Revenue: $700
Mortgage interest ($400) (I guessed)
Insurance & taxes: ($100)
Depreciation: ($63.92) (I used my rough number)
Taxable Income: $136.08
Using my numbers above, you should have only been taxed on $136ish, not the $400.
disclaimer: not a CPA, so you probably want to consult with one. Might be worth re-filing your old tax returns to get the tax benefits.