If you are looking to use the equity from the two current rentals, and do not want to sell them i would suggest a commercial loan where the bank simply puts a lien against the properties you already own, say for the $30,000. Then use that as an equity down payment on a $100,000 or so duplex or triplex.
I enjoy using these "equity grabs" for a couple of reasons:
1. I have no plans of selling any of them my current rentals as they were all bought correctly, and they all cash flow sufficiently (i realize this can change quickly but my bank will work with me)
2. it allows me to do 100% financing on my deals which means i am maximizing leverage with OPM (other peoples money) therefore your ROI is technically infinate.
3. i do not have to pay interest on an equity grab, it is just a lien against the property. Now, obviously you pay more in interest on the new property since you are not putting money down, but in my opinion this is a way to greatly accelerate your trajectory with real estate, if that is what you are looking to do.
This may not be what you are looking to do but it has worked for me so i thought i would share.
Thanks and good luck