It just crossed my mind the other day this is an option.

There are so many options and variables out there that I would definitely recommend you reach out to a lender for advice and guidance.

No pre pay DSCR options exist, but that rate will be quite a bit higher than conventional. 

I think what matters most is if the bathroom is nice, modern, and user friendly then either option will work. 

I think Columbus is a great option to consider.

There are tons of great DSCR brokers on BP but I would recommend getting in touch with an experienced broker who can quoted multiple options for you across all lending platforms.  

I would speak with a lender and see what your options are - also they will be able to tell you exactly what you would need to do to be able to qualify. 

I heard that families with small kids prefer one story homes because of children safety, that is why I am not sure if investing in a two story home is a good option even if it may be a less expensive option.

Those seem to be in need, as there are very few 5+ bedroom options. 

Weigh ALL your options.