With this in mind, how much cash will I need to generate $15,500 per year at 5% interest?
Sorry to put a dampener on things, but you need to take inflation and tax into account.
If inflation is running at 3% and you will be taxed at 20% then a $100,000 lump sum will generate at 5% interest will generate
100,000 * (0.05 * (1-0.2)-0.03) = 100,000*(0.04-0.03) = 1,000
This will maintain your capital and income in real terms, that is you'll always have the equivalent of $100,000 and if inflation, tax and interest rates stayed the same, you'd always have the equivalent of $1,000. Your tax rates will probably be lower especially if you don't have any other income, but inflation may be higher (the retail price index is currently running at 4.8% in the UK). You can also calculate in reverse:
15,500 / (interest rate * (1 - tax rate) - inflation rate) = lump sum required
In the UK, the tax on $15,500 income taking into account allowances and so on would be about 6.5%, a good measure of inflation is 4.8%, and I can get an interest rate of about 5.5% so to maintain capital I'd need a lump sum of
15,500 / (0.055*(1-0.065)-0.048) = $4,525,547