How does buying with partner affects Debt to Income Ratio?

[Mary Jay]

If I buy a house with my partner, lets say we buy a 300K house together.

How will lenders look at it down the road if I want to buy more rentals by myself? 

Do the lenders look at the house that I am buying with my partner as: 

1) The lenders will count 300K loan towards my Debt to Income ratio

Or

2) The lenders will count 150K towards my debt to income ratio (because I own only half the house/half of the debt)?

I am trying to avoid a situation when my debt to income ratio is too high to buy...I want to be able to qualify in the future and do not want the house that I am buying with a partner to cause issues getting future loans...

Thank you!