In the interests of 'protecting' first land, why don't you restrict resale of first land for 3 months after purchase. they can return it to you for the 512 during that time but cannot claim first land again.
The 'reclaimed' first land could then be released as first land again.
Helps new players get land, and keeps alts from claming profit as they have to be premium for 3 months (holdding the land) to resell.