What DTI is too high to get 2nd mortgage approved?

[Saman Jafari]

Hi all, I’m in a dilemma with 2 choices:

Either get a conventional loan w/ 5% down payment and get a residential place or buy a cheaper rental property in another state that flows more cash. 
even though the former choice would have a higher ROI, my question is whether I can get the 2nd mortgage approved to go for the 2nd choice after bought the residential home while front-end dti would already be at around 30% with having the first purchase. Do you think I can apply for the second mortgage after 6month/1year?