I'll try to hit the highlights but you may wish to speak to an accountant.
You should have been keeping records of your depreciation yourself. That kind of tax paperwork you need to keep as long as you own the house, even though there is a general rule that most tax papers can be discarded after 6 years, for houses the rule should be, keep your tax papers as long as you own the house plus 6 years after you sell. You can get copies of your tax returns from the IRS for 10 years, I think.
If you moved out on (for example) July 1, 2014, then the 5 year rule means that you would have to sell by July 1, 2017. The 10 year suspension on extended duty gives you until July 1, 2027.
If you are single, and you qualify for the exclusion, you can exclude the first $250,000 of capital gains from taxation. The trick is to figure out what the gain actually is. Also, any gain attributable to the period of time between 2005 and 2012 is non-qualified for the exclusion. This rule is not currently described well in publication 523, but it arises from the fact that if you move out, then move back in, you can't get the exclusion for that "out" period because the IRS doesn't want an absentee landlord to be able to convert all their gain to an exclusion by moving back briefly. As long as you don't move back before you sell, the period of time from 2014-2027 is qualified. However, if you do move back, all that gain becomes non-qualified as well, so if you really want to use the exclusion, you need to sell without moving back in.
To calculate the tax consequences, treat the property as two separate properties, one all-rental and one partly personal. Given your figures:
On the rental units, your cost basis is $250,000, depreciation is $65,000 and selling price is $500,000 after adjustments. (But beware what adjustments you claim, some web sites are quite wrong about what is allowable.) Capital gain on the rental side is $315,000. The first $65,000 is taxed as depreciation recapture (max of either 22% or 25%, I forget right now) and the rest is taxed at 15% or 20% for long term capital gains (depending on your other income).
On the owners unit, your cost basis is $250,000, depreciation is $65,000 and selling price is $500,000 after adjustments. You owned the property 24 years, but 7 year are non-qualified, so only 17/24ths of the gain (70.8%) is "qualified". Your overall gain is $315,000. The first $65,000 is taxed as depreciation recapture. Of the remaining $250,000 of gain, $177,083 is "qualified". Since $177,083 is less than the $250,000 exclusion, all of the $177,083 is excluded from your taxable income. The $72,916 of non-qualified gain is taxable as long term capital gains.
So in the overall deal (bought for $500,000, sold for $1M net, depreciation of $130,000); you will pay depreciation recapture tax on $130,000; long term capital gains on $322,916, and exclude $177,083.
I think.
Because this property is located in CA, you must file a CA state income tax return to report the taxable part of the income ($130,000 plus $322,916) and pay CA tax, because this is considered California-sourced income, even though your permanent residence is not in California any longer. CA doesn't have a discount capital gains tax rate, so it will be taxed in CA as ordinary income. (But CA does respect the capital gains exclusion which is $177,083 in your case.)
