here is based on some facts

1) no bank will give loan to your relative in China

2) hard money rate is 15%.  that is the alternative for bank loan.

3) management fee (pm fee) is 10% of rent and 1 month rent (or % based on rent) for find a tenant

4) assume your can get rate x% (x<15)

Than it is easy to calculate if this is a business negotiation:

you should get PM fee + (15% interest on loan - x% interest on loan). rest is your relatives.

The result could make no sense for your relative to invest in this deal.