Maddie,
You have a lot of questions. I don't know if I can answer them all but I do have something to add.
I assume you are going to live in one half for a while at least before moving on and keeping both halfs as rentals.
Consider the location and what type of resident will be renting from you, and being your neighbor. The two NE Mpls houses you linked have really bad school ratings. That will largely drive away a certain type of clientele. Young couples. room mates, and singles love parts of NorthEast. As do artists and blue collar workers. It is becoming hip to live there and still cheaper to rent than in Uptown. However, it will be difficult to attract families with school aged children because of the schools situation.
Anyway location matters more than price. There is a wide range of different customer profiles for each area you listed.
If I was in health care, I would try to find pockets near hospitals where there are more like minded people wanting to be close or within transit of the medical centers. Near the U of M, Richfield, and Powderhorn Park are areas that might be good options due to proximity to medical jobs.
To address some of your questions.....
1. Getting prequalified 5 months before you move does not really make sense. It will not work. You will need to be prequalified again in May, or whenever you are starting to shop. You could consult with a mortgage broker now however to understand better what types of loans and properties you should be targeting. You cannot lock in an interest rate this early.
2. Best deals buying in a hot sellers market like we have today is to intentionally buy a fixer upper. Buy one that needs some work and you will definitely reduce the competition.
3. If you fix up a property top to bottom with an FHA 203K loan, your ongoing maintenance cost should be manageable. You would be able to easily plan on 5% of gross rents to cover anything that comes up. Then - plan for capx like roofs, windows, driveways, siding, HVAC systems. You should inspect these when you buy with an estimated date of when they will need to be fixed.
4. For reserves, 6 months is not a hard and fast rule. I would budget for 3 months of expenses due to lost rent and for having to replace carpets and paint if the renters damage your property above what damage deposit you collected.
5. For vacancies, you can plan on 5% for vacancies as long as your property is in good shape and you carefully screen applicants. If it's been renovated and in a good school district, you should never have more than one month of Vacancy on average every 2 years.
6. Make sure you can cash flow after accounting for all of the expenses and debt service. Doing this math is eye opening. Make sure it will cash flow after you move out and both units are rented.
7. buy now or later? I think interest rates will go up - but if they do, values will go down accordingly. Its probably a wash.