This lherng making a lot of assumptions that property prices can go up  to cover interest rates and exoenses.

This is called being generic. You make statements that are "high level" and non specific.
He cannot offer you specifics , or else if it doesn't turn out well , his prediction will be proven wrong black and white.
It's the same with any investment vehicle.

If you choose a good company, the shares will go up big time .
If the company has good management, the shares will go up big time.

To me statements like this has really no value.

For eg:-

If I bought Nvidia 10 years ago .
Notice if you use a generic high level statement, he can show that he is right regardless of the outcome.