Commingling Funds - is it legal?

[Kenny Wolfenberger]

At a recent real estate seminar I attended the presenter said that it is illegal to commingle funds from different private lenders to purchase a property. The example he used was borrowing money from 2 relatives (50% each), sticking it into the same bank account, and then using it to pay for a property.

Is this really illegal? If so what are some ways to get around it? Any additional explanation of the laws related to this topic would be much appreciated as I haven't been able to find much Googling.