Ideally my brother and I would buy the property together and form an LLC and run as a business.However, my wife doesn't want to enter a "business" relationship with my brother, but instead suggests that we purchase the properties individually (since they are both on seperate deeds).

I think we all try to help each other but at the end of the day you have to make sure that you don’t over expose or extend yourself as an individual.

Ask them if they will lend on line 120 of HUD-1 (..pretty sure it's 120) This process is a bit out of the box, which lenders are not usually a fan of.

As @Lee Ripma mentioned "Set For Life" would be a great book to read.As far as choosing the right market... you can read several reports online (just search google for XYZ city real estate report).

I’m looking to open an online account with vanguard, TD Ameritrade, E*Trade, or maybe even the Robinhood ap with my checkbook sdira to buy REITS.

The concept of reasonable is really on the individual, because your reasonable may be $500,000 vs someone in the midwest reasonable may be $100,000, so you have to find whats comfortable for you, do your hw and take action. 

Can anyone recommend an easy to use online payment app or method for allowing tenants to pay online and direct to my account?

Lease docs, contract docs for when our clients buy/sell houses, anything we need signed is done through there.Giving tenants the ability to pay online or with a card.

I've done a lot of research on it online, which is possible here, and even gone to see it (pretty recently renovated!?).

My issue-situation-question is this: Because we have made REI our goal, with a plan for a lifestyle change, business objectives , and everything, we are online every day looking for and analyzing deals [as you can see I upgraded my BP account to have full access to the calculators!!!