You will get better answers in the RE forum.
That said, more information is needed here.
-Do you *need* to tap equity to buy the rental properties? Talking with a mortgage broker may be a good idea here since what you can qualify for and what DP you need will depend a lot on your income and situation.
-Is each home worth $350k, or are they worth $350k together?
-How much are the rental properties you are looking to buy?
I will generally say that if your entire NW is tied up in illiquid assets (in your case, RE) tapping equity to further leverage yourself may not be a great idea - you will need oh-crap money for when the roof has to be replaced or the boiler floods the basement and steams the paint off the walls of the house, or whatever. If you have liquid assets as well (ie stocks/bonds/cash/etc) sufficient to cover unexpected repairs simultaneously on several properties, then a home equity loan would be a fine way to go assuming the numbers work.
Posting more specifics will lead to more useful advice.
-W