My house is in decent shape, but I don't know what the lifespan of a typical aluminum roof, AC, and other common features for a house in Florida would be.

On top of, typically, higher vacancy as you wait for a qualified tenant to apply.  

---So, learn the neighborhoods where you plan to invest and use Google Streetview to virtually explore them.3) Poor Tenant Screening - they typically can't sell a property until they place a tenant.

Here's an example I used many years ago:"I'm interested in a cheap fixer-upper single-family home under $100,000.

Exactly.Last time I counted, I had 23 business bank accounts, and while it can sometimes be a pain in the butt (for example, I have about 11 different checkbooks), at the end of the year, it makes accounting much, much easier...

Examples: buying the run down property in close proximity to yours, filling a vacant commercial space with a neighborhood amenity near residential units you own...these are just examples.

Also, to give you an idea of how the math works here is an example based on your home's values:If the lender lends up to 80% of the home's value, the maximum loan amount based on 80% LTV would be $392,000 = ($490,000 * 0.80).With your existing mortgage balance of $390,000, the remaining available equity for the HELOC would be $2,000 = ($392,000 - $390,000).Hope this helps!

For example, if it costs you $50k to build, and the house appraises for $100k then you will have $50k or 50% equity.

I initial brought it up as an example of the type of current information I use to assess current market values which I would gladly provide feedback on properties.

However, lots of CUs and Locals are requiring you to keep deposits with them if you want a loan - typically around the 10% mark.