Can the buyer add to an MOU a clause to avoid any unforeseen incumbrances?

Hello,

I like initial advice from a legal professional before proceeding with the sale of a shop.

The buyer agrees to pay a deposit and sign an MOU but wanted to add a line in the MOU that if anything we hide or not disclose which he finds later - he will eligible for a deposit refund and a penalty from us.

Now we say no to this open-ended clause right away. We provided a credit report, court letter, accounts everything to his due diligence representing a company but he still wants to add this line to make it risk-free.

We thought no deal like this open question can be accepted anywhere in the world.

Kindly advise

Thanks