brandino29, I have the same idea as you, so if it is Lunacy, we both are afflicted. First my thoughts on primary mortgage requirements. When we re-fi'ed last year we carefully read that we have to live in our home for a minimum of 12 months, it was very clearly spelled out on one of our signing documents. So you should be able to find a mortgage with similar terms.
Since that Refi, we've become new landlords, but we had already researched and committed to that particular FI path and are under contract for property #3. So far with the first two (duplexes so 4 doors) the total cashflow pays for ALL of our basic housing expenses and that's a great feeling. #3 will pay for (cars and food) and down the road #4 is our fun money and medical.
We might end up in a pickle if landlording is not our thing, but our skill set is in everything home maintenance/repair so it made sense in our situation to commit to it 100%. At first I was thinking of turning our residence into a rental, but we love it here so likely we will continue with duplexes until we have 4. That will be our FI jumping off point.
Like Meadowlark, I also found getting a mortgage painless and quick using the same local lender (3 mortgages in 8 months), so now I feel I have a relationship with them in the event we want to go for 5-10 mortgages. If our circumstances were different I would prefer to acquire more slowly and live in each unit along the way. Unfortunately age and medical issues altered that plan.
If you go the "live in it for a time" route, you get better rates, can put much less down, but your cash flow will be lower as well. It will also have a fixed timeline. I suggest you fiscally map out your game plan both ways. It will be a trade off of time vs. money. We are impatient and are looking at ways to shortcut our acquisition time.
Because of the mustachian education this site has provided, I have changed things up for #3 and am going for a cash deal. I found low interest cash options lurking about that took me time to sort out/find/become comfortable with using. Once the ball is rolling you will be amazed at the new paths that open up to you. It is akin to finding money under a rock. What a surprise it is to find out that decisions made long ago have ended up providing money now when we need it.
I agree with Meadow Lark, stay positive, this should be a fun journey, but definitely research, research, research and then research some more! I might be singing a different tune in a year, but so far have enjoyed the ride!