That depends on where you are. Your post is tagged Seattle but then you also say you have 10 acres so I suspect you are outside of the city. Buying in Seattle most likely won't help you with your DTI, at least immediately, since barely anything cash flows in Seattle as a long term or even a mid term rental. A short term rental, as others mentioned, will need to show up on your tax returns so there is some time there as well. Building a legal DADU will again depend on where you are as local rules vary.
If I were you, based on the very limited available info you provided, I’d build a DADU just to dip your toes into being an investor and a landlord and then see if you enjoy that experience (or if you are in a more remote area, buy an existing cabin near you and short term rent that). It’ll be close to you so it’ll be easier to manage…Once you have some investing experience, you can look at all the other available options.