Am I getting screwed?

[Ashly B.]

We made an offer of $95k + seller to cover $3k in closing costs for a 4 plex on May 8. Seller accepted the next day. Realtor apparently forgot to put the closing costs in the offer and no one noticed until now when the bank is drawing up the paperwork.  Our realtor admitted it was his fault and sent us an addendum yesterday stating that the costs would come from his commission. I was a bit confused because I wouldn't think his commission would cover $3k but I wasn't out any money so I signed. Today I get a second addendum with a note that says the bank doesn't allow seller paid closing costs to exceed $1900 on investment properties. 

I've never heard of this rule and it seems ironic that it just happens to be an amount low enough to where his commission would cover it... can anyone weigh in? Is this a real rule or is he covering his ***?

Regardless I feel pretty peeved that if this is a rule, my realtor wouldn't have been able to advise on that.