I am thinking about actively trying to grow my investment portfolio and use my existing properties as leverage to acquire more properties.

One great tip I received from Rob Abasolo is to invest more into your existing property to maximize revenue. 

So if you buy and rent out a retail center or an apartment building or increase the existing income the property is going to be worth more and can be refinanced easier.

But they're going to require you to refi the entire amount (i.e. they'll refi the existing loan of 1.2 and add the 200k for rehab for a total loan of 1.4). 

If the owner used a Texas Association of Realtors(TAR) lease, a provision exists for finding a replacement tenant and charges the tenant with a % of one months rentEdit : Fred types faster than me !

Basing estimates of rents and expenses based on my existing knowledge of local markets.

Every marketing channel works (SEO targeting duplex sellers,  PPC,  cold call center, direct mail), and thats why they exist. 

They can also be available in existing neighborhoods in infill lots. 

These are not typical life insurance policies.If the down payment comes from an existing asset whether it is money from money market, money from savings account, money from CDs, money from heloc, money from selling stocks, money from stock margin, gift from family, money from life insurance it does not achieve a 100% LTV with respect to determining return.  

As an extra level of protection You could try and save up a few months of what the potential mortgage will be to give you peace of mind.