I am 17 with cash on hand

[Andy Park]

I am currently a high school senior in Georgia about to graduate. I came into high school with the goal of being in a position where I have enough cash to buy my first investment property when I turn 18 (I turn 18 in August). Through working, investing in stocks, and saving absolutely everything, I am in a position where I have a good amount to work with (a downpayment of 100k-150k, but depending on the opportunity more can be scraped up). I have been discussing this for years with my parents, and my dad has agreed to cosign for a loan (he has a credit score of over 800). As of now, I realized the next step for me is getting preapproved for a loan. Should I wait until I am 18 to talk to lenders? Even if I have a cosigner with excellent credit, will I still have great difficultly in getting preapproved due to my short credit history and age? I am all ears to any advice and suggestions for the next steps in my real estate journey. 

Thank you,

Andy Park