If you read Million Dollar Agent, Gary Keller emphasizes obtaining listings as the primary focus to building your practice. 

Using as a primary residence once the rehab is finished.

Not a lawyer or anything, so I'm sure someone else can explain more on differences if you have a chance of life event or something, but this is is straight from the 92900B that you will sign in an FHA purchase loan:"Do not falsely certify that a property will be used for your primary residence when you are actually going to use it as a rental property""Penalties for Loan Fraud: Federal laws provide severe penalties for fraud, misrepresentation, or conspiracy to influence wrongly the issuance of mortgage insurance by HUD.

Really, there are 2 primary models (I'm sure someone will disagree with me here, and that's ok!)

Even more obvious when a real name Google search lands on this post.Your other angle of buying an investment and later trying for FTHB on your primary is a great idea and one you should check with a tax pro on (ie, not HR Block).If you can use the plan, then start cramming every dollar you have into an RRSP so you can use that money tax-free come time.

@Evan Greenfield:I'm a buy and hold guy....Neptune or Atlantic Beach area is primary.  

@Yadira Gutierrez You never mentioned a construction to perm loan....wrap your primary and do a hard core rehab or build a house...good times. :) Best of luck in whatever you decide!

I'm planning to apply for mortgage for the fourth home as primary residence(CA), Will I be able to have mortgage interest deductible since it will be my primary residence?

Since you'll be "flipping' your primary, how will that impact your other flip(s)?  

I currently own my primary residence worth about 90,000$ I also own a rental property out right worth 110,000$ I currently recieve 650$ a month for my property after the management free.