BRRRR ? Refinance questions

[Michael B.]

Questions about refinancing.

I moved into a property at the end of may this year.  The house was purchased for 130k, it appraised at 135k.  I got a conventional loan with 5% down, 30yr and took a 4.25% vs a 3.75% to receive about 2500 back in lender credits on my down payment.  I'm very green as far as mortgage tips and tricks as this is only my 2nd mortgage.

I'm currently updating parts of the house such as a full bathroom gut on the main floor, new water heater, softener, fuse panel, radon mitigation system, windows, paint, flooring etc.  When I got the house it was just overall tired and In need of someone to come in an do some maintenance. 

Goals

-Refinance soon-  I planned on going 15yr with the lowest interest rates I can get with a credit rating about 740- Yes I feel more comfortable getting stuff paid off quickly rather then having lots of 30yr loans

-Build 20% equity with improvements prior to refinance

-No more PMI !

-Turn the house into a short-term rental when I move out next spring/summer and finally have my first Investment property!

Questions- Mind you I'm very new

-Any problems refinancing this quickly? 

-80% equity enough for a refinance?- still owner occupied at the time of the refinance

-Does it have to be owner occupied for any length of time after the refinance?

Anything else you want to add I'm all ears.