Appraisals used for Cash-Out Refinance

I'm researching cash-out refinancing for some properties that I own free and clear. I've done some poking around in the forums and see the main challenges you have experienced with doing this:

1. Seasoning period: 6 months, and sometimes up to a year

2. Sometimes the the cash-out is based on the purchase price rather than the appraisal.

I haven't found much information yet on the actual appraisal so I have a few questions. My properties are located in Michigan state:

1. Does the appraisal often come out pretty close to the comps? Or is it common for properties to get under-appraised?

2. Is there usually a minimum appraisal value for a cash-out refinance? For example, if I have a SFR with appraisal of only $30K, will some banks refuse to do it?

Thanks for your help!