There's no "right" choice unfortunately.
The question is, do you borrow at a low rate and hope to achieve higher rates elsewhere (stock market, investment properties, etc.)? Or do buy a home in cash and content yourself with a low, but safe "return" (the "return" here will be the interest you don't have to pay on the loan). This is going to come down to your attitude about risk. You might decide to split the difference and put down 40-60%.
With respect to whether or not to invest in rental properties, you'll have to do your own research. Read some of the resources listed in the sticky thread in this category, and decide if it's right for you. At the very least, you'll probably want to start with one property, perhaps at a more modest leverage ratio, rather than buying 5 properties right out of the gate levered 5 to 1.
Basically, you're going to have to do a ton of learning on your own about real estate investing (and perhaps personal finance in general). Advice from friends and people on a message board can only get you so far (and might even be dangerous is it gets you into something you don't fully understand).