Not a good idea as he sacrifices €6,500 a year net for two years or €13,000 up front.
After two years, the legislation may well be changed and he could be stuck with charging the same rent.
After two years, rents may have fallen so he might not be getting more than €1,300 a month.
If he is still unhappy in two years, he can sell the apartment and buy another one which has not been let and charge market rent. Or he can do that now or just exit the market as many landlords are doing.
Sinn Féin is proposing to require landlords who want to sell to be forced to sell with the tenants still there. So it is probably time to get out anyway.
Brendan