This is assuming you can locate properties of lower class in higher rank areas.As to weather B or C area is better, the way I look at it is the following factors:Yield: What are my investment return goals, naturally higher risk, C areas will produce better yield. 

You need to be able to manage and deal with multiple contractors and vendors who don't always produce what they say.

Bottom line, it comes down to how active you want/can to be with your investments and what returns it will produce based on your time devoted to this business.Here're a few articles on the topic for you:https://www.biggerpockets.com/member-blogs/10850/84064-what-type-of-investor-to-be-when-i-grow-up-active-or-passivhttps://www.biggerpockets.com/member-blogs/10850/85836-should-i-buy-a-turn-key-property-or-invest-in-a-syndication

Trying to figure out whether Air BnB or traditional 6-month/12-month leases will produce better monthly cashflow.Very excited about this property as it's located near several Federal economic engines as well as being a 19-minute drive to both Amazon HQ2 in the Crystal City neighborhood of Arlington, VA and the accompanying Amazon Warehouse in Westphalia, MD.

Trying to figure out whether Air BnB or traditional 6-month/12-month leases will produce better monthly cashflow.

If you're looking to get into an investment property, I'd be thinking about evaluating your 2nd property with your nephew separately (ie: what to do there, is the property producing income like you want, its long term appreciation prospects, etc)Hope that helps....

Craigslist, MLS, FSBO, etc. will not produce what you're looking for unfortunately.

I think your first step @Stephanie Yi is to educate yourself thoroughly on different passive investments that produce consistent income.

How to take alot of loans, im not from america so it might work bit different for me but what is general procedure also if i take on example 30y loan with like 20% downpayment can i take another one if i have like 20% downpayment for new one or banks wont give me another loan till i pay this one off.

I have specialized an income-producing properties for 30 years.