How to go about buying first-property? Found one but have never purchased before

[Evan Alexakos]

Hello,

As the title says, I have found some properties that look to work in terms of cashflow and rate of return but I've never actually purchased a property before. The math works out online and tenants already live in these buildings so I know they are liveable; that said, I have not visited the homes or made contact with the sellers. 

How do I go about starting the process of buying a property?

How do I get pre-qualified for a mortgage?

How do I get official approval for a mortgage? (Can I use the estimated cash flow of the house as proof of income for mortgage applications?)

One property said they would consider seller-financing to a buyer, do I contact the seller and ask?

Thank you for any replies.