18 year old investor/realtor seeking info on morgages

[Kevin O'Brien]

Hello,

I just turned 18, graduated from high school, finished my Indiana Realator license and am enrolled in a construction management program at Ball State. When I turned 16 I started my first business which dealt in gold and silver bullion. This allowed me to save money to invest in real estate when I turned 18 however I have minimal past income. 

Additionally, my parents are giving me the option to receive a lump sum payment to go toward possible rental property purchases. This would be an alternative (and lower amount) to the predetermined amount they would contribute toward each semester of college tuition. I plan on taking this option and using the rental income to offset what they would be contributing.

By having my realtors license I estimate I will save 2-3% on properties and aim for a few more percents toward closing costs so I only need to pay 20% out of pocket for down payments. My parents have always told me that I need to expect to put 25% down on investment mortgages. They have a combined 45 years of experience with rehabs, new construction, and commercial in Chicago so I have naturally learned a lot from them over the years and tend to trust their judgment.

My questions - 

Is 25% down overkill? (if so where should I look for investment mortgages with lower down payments?) I am looking for traditional 15 and 30-year mortgages.

Will I need cosigners for properties if they cash flow 1%+ a month after all expenses and a 25% down payment 

Also, any references for mortgage brokers or bankers that actually write up these loans in the Indianapolis area would be appreciated.