I'm just stuck on this situation because our borrower is putting the funds back in their personal savings account. So should I look at it from the point of view that the funds going directly into his personal savings account as consumer purpose without worrying over why funds were pulled out to begin with? Or, should I look at it from the stand point that a very commercial event occurred that triggered the need to replace funds in the personal savings account?)
You are right that this is challenging scenario and I too can see it going both ways, depending on the circumstances. The question I think you need to answer and seem to be missing (at least in what you wrote) is this: why are they putting the funds back into their savings account?
To answer this question, consider this:
1) Are they putting funds in their savings account because they always intended to
finance a rental property as Joker has explained? If their intent was always to finance the property, but couldn't do so initially because of timing (like the scenario Joker gave), then I agree this is commercial purposes. The loan with you is sort of paying off a commercial loan they gave themselves (though of course it isn't really a "loan" when they are a sole prop and co-mingling personal and business purpose funds).
2) Are they putting the funds in their savings for the purpose of
increasing personal savings and, if so, why? I have seen some loans where a rental property was purchased some time ago (maybe a year or two) with cash and the borrower now wants to use that equity to buy a lake/2nd home or pay for college. In this case I would call it consumer purposes. Other times, a sole proprietor might have a purpose of
replenishing cash reserves to buy another rental property. In that case, I would (probably) call it commercial purposes as the reasoning for the cash is to position themselves to purchase a rental property.
3) What was the timing with the purchase and requested loan? If it was close in proximity, it would seem that Joker's scenario is probably correct and this is a commercial loan to "finance an investment property." If not, you may need more information as to the full intent of wanting to increase their savings account.
Regardless of what you do, make sure that your documentation clearly supports your decision so that you can avoid future criticism as, like I said before, I could see this going either way - depending on all of the specific facts and circumstances.