Help! I don't know what to do!

Case: What will you do if your boyfriend asks you if it is ok with you that his ex-boyfriend be his housemate? I mean, he'll let his ex-boyfriend rent one room in his pad. What will you do? What will be your initial reaction? Will you let this happen? Why?

Note: Both of them are in good terms. It has been 3 years since they broke up. And both of them still keep in touch.

HELP! :(