First Deal- Build and Rent

[BP K.]

Hello all, 

This is my first venture into REI and I'm seeking wisdom about potential pitfalls/things to know or avoid in this scenario. I'll try to keep it brief!

1) We are looking to build a house next year

2) Our plan is to attempt a cash-out refi of our existing mortgage (the equity will be used for down payment on construction loan) 

3) We would then seek to rent out our current home once we're ready to move into the newly constructed home (understanding this would require us to notify the mortgage company). 

Current market value of home: 150,000

Current principal balance: 100,000 

Are we losing some equity by doing a Cash-Out refinance vs just selling the home?

Thank you all!