To enter a NR4 slip in TurboTax, you would have to
look at the income code on the NR4 to determine where the amount should go. So
if you have Code 13 income, you would fill out a T776 to enter the rental
income, then you can put the taxes you paid on Box 22 of a T4A slip.
I don’t think you would need to do 2 separate
returns, but you may want to contact the CRA to confirm. If you are in Canada
or the United States, you can call the CRA at 1-800-959-8281. If you are
somewhere else you can call 613-940-8495. Here are more ways to contact the
CRA:
https://www.canada.ca/en/revenue-agency/corporate/contact-information/telephone-numbers.html