Reaching out to the BP community for  recommendations of tax and legal professionals close to my area specializing in real estate investing. 

Nevada is also a landlord friendly state with low property taxes.

They can ensure a smooth transfer and advise you on potential legal and tax implications specific to your situation.

The owner wants to minimize the capital gains tax he pays so we want to suggest to him to do a master lease to us for "x" amount of time, and we pay his lease fee and hold the rest of the money in this time we will secure a loan to buy using the money we make as part of the down payment.

my wife would assume the loan, and quit claim deed her mom off.

I have heard that I should have an LLC for each home but it seems administratively burdensome to have 100 bank accounts and 100 different tax filings, credits cards, checkbooks, etc...

What that really means that I can't claim the suite as a separate apartment (a.k.a. not a duplex); I could not add a range/oven for cooking.

You can run the Osha 30 Hour Course on the background of your computer, obtain acceptable levels of insurance and as long as you don't owe the city of Philadelphia taxes, you can get a General Contractor license in Philadelphia.

What tax benefits might you receive that could potentially offset some of your tax burden with such high income?

You make money and are expected to pay taxes.