The system is simple and, thus far, largely unavoidable. When a user attempts to make a post, Craigslist asks for verification with a viable phone number. It then automatically calls the number and issues a verification code which must be re-entered for the post to go live.
For the purposes of the IRA distributions, a first-time home buyer is anyone who hasn't owned a present interest in a main home for the previous two years. For example, if your parents have promised to leave you their home in their will, that isn't a present interest in the home, so you still qualify.
A first-time home buyer for the D.C. tax credit is defined as someone who has not owned property in DC during the one year period ending on the date of the purchase. To claim the credit, use IRS form 8859 District of Columbia First Time Homebuyer Credit.