Do they have 20-25% down to ask for seller financing?

However, as I walk down the street in my city, I see tons of retail businesses that definitely do not comply. 

. $120k out of pocket money down to obtain the funds.Huuuh???

Were I am getting disappointed is the lenders for Commercial say you need 20% down payment (I don't have that) and when I tell them if I could have Seller finance in the same deal, was told no.

We put the 20% down, but then life happened.

If you are moving from your SFR to another property, then you should be able to get a 5% down loan or even 3% if it's FHA.  25% is only if you won't be living in the property in my experience.

If you're younger then it might make a ton of sense to take down anything you can as long as it cash flows. 

refinance our own home with some money down + purchase another flip? 

Sit down and hash out every detail and put it in writing.

There are some lenders that brokers can work with that also get down to Prime (7.5% as of today).