How to get first mortgage on rental investment

[Sean Forner]

Hello everyone. I was wondering if anyone could lend their advice and give me some general direction towards obtaining my first loan that I will be putting towards 3 single family homes, which will be bundled together for around $150,000. I am 22 years old and just graduated from university last week. I have just recently accepted a job offer from a company I interned for that winter and will be making 36k this year. I have saved $30,000 dollars and have no debts accept for $19,500 student loans that I don't have to start paying off until December with a 4.5% interest rate ($220/month). I also have a 720 FICO credit score and will be living with my parents rent free for a year. 

With that said I have a solid credit score, decent income, enough for a 20% down payment, and little debt. However, I have not had stable employment for the past two years, but have worked/held internships every summer and winter since starting college (September 2012). Now the investment on the houses is solid, I just need the loan and am willing to accept the 4-6% interest rate that comes with investment properties.

What is my best course of action to ensure I get the mortgage by mid July (month and a half)? Some final notes are that my father is willing to co-sign or co-borrow on the mortgage. He has been employed in the same industry for 35 years, has an income of 100k/year for a company he's been working for 10 years, a credit score of 740, and a good debt-to-income ratio.

What would you recommend I do? For anyone who replies, I sincerely appreciate it.