Take maximum mortgage amount available or only as much as needed?

[David S.]

Hey guys! Looking for advice on a good problem. My wife and I are talking to a lender for an addition to our primary home; we're adding a 3 stall garage with a MIL suite above it that we intend to rent out along with use of half our barn so the tenant can board a horse on site since we don't need the entire barn. It's likely the best way to unlock the value in our property; call it a house and farm hack. 

In speaking to the lender we qualify for more money than we need. If we take out a mortgage for the maximum amount offered, it would leave us with an extra $150k that we could put to work. I'm in Denver but have been scouting the KS City market for a while with an eye on starting an out of state rental portfolio. So this could be a perfect scenario of creating two rentals off of one loan, all using the same origination and closing costs as well as appraisal costs. If I don't use the extra money right away and park it in a CD my holding cost would be $300-$400 a month till I do use it. 

What would you do? Take out the larger loan to pull the trigger on a rental in KS City AND do the addition, or focus on the addition first. I have baked in an extra $50k for unforseens and overruns fyi. 

What considerations come to mind for any of you finance and mortgage experts? 

Thanks kindly!