When you say a "safe" home does that mean safe neighborhood or safe as in code or physical status safe (hazards, etc.)?

As they say a confused buyer is not a buyer at all! 

A mortgage with 3.5% down at say a 4% interest rate (this is an aggressively good rate, it could very well be higher), is $1405.

Over the course of 10 years you are able to pay the mortgage down from 225k to 195k and the house has appreciated, let's say a conservative 3% a year for 10 years and now it is roughly worth 403k.  

I mean, if I start with a property, let's say a single family, costs 0.7 X and I do a minor rehab that increases the price after repair to X dollar, I am wondering if what number of similar property is a reasonable number after 5 years?

I would say a majority of thaht 3% 30 year debt is in SFR and those notes were ALL sold in the secondary market China is holding the bag  LOL

The only time I’ve seen it used is when someone owns a California property for 20 or 30 years and has say a $1million gain.

What should I say as a new investor that's first starting out??

Basically give me an example of say a $100,000 home and how this is wise to use that rents for $1200-1400. 

Remember an investor is likely to pay 60-65% max of the ARV on a fix & flip, might go for more on-market with an end-buyer over an investor if a conventional loan would work on it (decent condition, good neighborhood, etc).I would say a developer buying for $160-175k (60-63% of the ARV) is realistic with the ARV of $278k if it's a simple fix & flip, meaning if your seller is selling for $90k, you would make $70-85k on this contract by selling at $160-175k.