The last I heard it was four "conventional" investor loans. The key word here is "conventional." Don't forget about alternative financing methods. There are too many methods here to mention, but just to list some, seller financing, hard money loan, and the list goes on.
Also, I have experienced that some portfolio lenders, lenders loaning money not conforming to Fannie Mae or Freddie Mac guidelines don't have to participate in the maximum four loan rule. You're probably counting your primary residence home loan for the 3 investor loans you mention in your question.
If you have (or set up) a self-directed IRA or 401-k, there is no limit to the number of loans you can get to purchase real estate held by your IRA and protected from "creditors" and from "capital gains taxes." For information on that, Google Entrust or Pensco.
You just have to "think outside of the box" in times like this.
Keller Williams Realty
Changes are coming in February to all of this so it's best to talk to a lender.