My perspective is certainly around the rehab world though.Leverage allows me to stretch my capital into more projects.

If a building is half paid off, should I re-mtg and take the equity out for a new property and stretch the new mtg out to 25 years again.

This is really the only way I see you stretching the $30k further there where it sits now. 

I wouldn't stretch it more than 7-14 days.

35 is not old by any stretch of the imagination. 

(a lot of my clients have maybe 100k cash saved but make 20k a year and live in Pasadena, ca where a fixer upper costs about $650k) : they really want to get started in real estate and are looking for every way possible to pin-point a place where they can stretch their 100k... so, one of the conversations I have with them is: how can you invest a portion of that 100k in yourself to increase your income. maybe schooling, maybe starting a business, maybe a course on whole-selling- or all of the above on whole selling.... but it is very difficult - not impossible, but difficult to create an empire with 100k saved and making very little income). * the alternative: you learn, you research while investing in yourself, and then getting a better job or business that pays you $50k, $75k or $100k + per year.

My only addition would be to make sure you're conservative on your ARV, and can justify the value to the investors you're pitching deals to.For if you fib a little and stretch to make the numbers work, you'll start to get a reputation as the wholesaler who has no deals and is simply full of hot air.When you're just start out, people are going to be double-checking your numbers every time, so make sure those numbers are right so investors will feel comfortable working with you.

This is first because the only home owners who lose over the long term in markets like SF are those that stretch too far financially and are forced to sell at the wrong time or give it back to the bank.Beyond that, I'd identify the sub-markets that seem to have the types of properties you need in budget.

I thought the water on the floor after my showers was "user error" but despite my diligence in making sure the liner was stretched all the way across and tucked around, the water kept appearing... in the middle of the tub length no less.  

If you have to stretch too much to make a deal work, it probably isn't that great a deal, at least for you.