They wanted $1.2M to payoff  maturing HML on a $2.5M property. their credit was 580 and we told them we would not give you a loan but we would buy the property from you for $1.2M, provide you with a 12 month lease with an option to buy. in 12 months you either buy it or its ours. 

What documents do they require, what credit scores do they allow, how do they verify previous rental history, etc.?

When you go to a Bank or Credit Union, they can only offer you what products that bank or credit union offer.

I would look at it in terms of whether you can afford a worst case scenario where you're covering the deductible and have a credit line or cash to front the re-build cost and getting reimbursed from insurance afterwards.

I have also have saved almost $50K so far to take a start in this game and also my personal credit score is above 750.I'd like someone to guide me purchasing my first property and want to kickstart with a small property first.

If you are running a LLC for your rentals is essential that you keep all business  funds in a separate account I like Credit  unions the best .

At this point, I would recommend having a line of credit to cover these things so you don't have money sitting in the bank doing nothing when it could be put to work.I have 33 units, no debt except for mortgages, and excellent income.

So I get this referral from a relative about a tenant who has good credit score, no criminal history, and a good paying job.

Credit unions, banks, mortgage companies and private lenders.They all had the same answer.

We purchased this as a BRRRR on a Line of Credit, went to do a few fixes then refinance.