I am no expert by any means but I thought I would drop my opinion here. 1) Should I focus on duplex since they're most likely less expensive in my area in category A or B properties, or aim for more units?

I'm not sure why not - one of the great parts about real estate investing is that you can build a team around you for aspects you aren't as strong at or simply want to delegate to someone/expert and do the others yourself - look up "Core 4" for example - where you can have an agent, lender, manager, contractor all at once for your investments and can theoretically just let them do all the interactive work

If you aren't an excel expert I wouldn't bother trying to make your own or scour the internet for an analyzer tool that may or may not meet your needs. 

I'm not an attorney or expert in AP specifically, but do have a working knowledge of it for Civil engineering/survey work and have had two projects where this came up and I was able to 'ride along' and see how it unfolded.First, if you 'know' the property has been taken by AP then there's nothing for you to do with the tax assessor etc.

@Josh Green is the local expert there. 

I think I'll start out where I live and probably branch out outnof state once I build my knowledge and experience. 

@Mario Morales, to echo Bradley, I would say this depends on what you are lacking in your own knowledge base.To some (probably many investors) the agent is simply an initial filter for them.  

I've thought about commercial real estate and/or residential house building but dont have any knowledge on where to start.

I am starting my first househacking deal this year and I will Segway that into my second deal by end of 2025.I would love to hear all you experts and pros with experience to tell your story.

I'm Igor - a revenue management expert with over 10 years of experience in the hospitality industry.