Wow! You have a great plan and if you keep learning and stick to it, you will be financially free long before your goal date. Id stay in college so long as you love what your going to school for and get a job doing that, then get an FHA loan for a househack. I really wish I would have learned that before purchasing my first property.
Neighborhood-I like B and C class neighborhoods, some would classify my properties as being in a C+ class neighborhood but in my market it really is street/block dependent. Which is also why it helps to have a great realtor who knows the area.
Size- Im with you, 3/2s typically work best for rentals- better tenants, less turnover, Higher ARV.
MFH- 2/1s are fine just be sure you use a higher vacancy rate when running the numbers. Ideally 3/2 but I wouldnt pass up a multi family property because it was a 2/1 on each side.
Lot sizes dont really matter too much IMO unless it is a really small lot or really big.
Property Condition- This is where your research and market knowledge really come in to play-another reason to have a good realtor. Ideally starting out you should get something with light cosmetic updates so that you have less risk if you go over budget or if it does not rent out for what you expected. But IMO if you are looking to build a decently sized portfolio, You could get a pretty run down property that needs full updating, BRRRR it, rinse and repeat. This is a lot harder than it sounds however. This is why you start small. If you have no idea what any of this work costs, what the property needs, or what the ARV and rental value is then you will be taking a massive amount of risk.
Cap rate-is mainly for large multifamily IMO, I analyze my deals by using COC return, and my goal is 15% AFTER BRRRR-which is easy, but I still would like a decent return in monthly cash flow as well so wont refinance to the full value of the property unless it still cash flows 500/month after expenses. ( on my current project).
I base my investments on what I like to do and my personality. I wouldnt like to call my tenants asking for their rent ( I would if I have to) I prefer a tenant who is low maintenance and pays on time every month. Not saying that all MFH tenants are like this but statistically there is a higher probability of a late payment when compared to SFH. You are correct though, multifamily is good for scaling. At the end of the day it is all about knowing your market very well, and then taking directed action to acquiring properties that meet or exceed your criteria in your market.
Once you are super confident in analyzing deals and ARV and cost to rehab/hold the property, and you find a good enough deal, financing will be the last of your worries. However IMO a job is crucial to being able to get loans on properties at least in the beginning. Keep learning, read as many books as you can, and start grinding, your young enough that if you start investing now, you will be lightyears ahead of 95% of people your age!