It won't be illegal, because the law has certain requirements for loans. The decoration company loan is the behavior of the decoration company, and the responsible party of the loan is the decoration company.

As for whether the decoration company helps the owners, it is a matter between the decoration party and the owners.

It can also be that the owner entrusts the decoration party with a loan, so that the legally responsible party is the owner and the decoration party belongs to the intermediary to help! However, the decoration party has no right to sign, and some supporting documents need to be signed by the owner himself.