Investment properties refinance

My customer wants to refinace two of his investment properties.  His mid score is 521 but his doesn’t have any lates on anything within the last 5 years he just has a lot of credit.   The value of one property is $21,000 and the other is $26,000.   He doesn’t care about cash out as much as he cares about lowering the interest rate, hopefully 10% or lower.   He also wants to purchase another investment property with 100% financing.  I don’t think that is possible but you never know.  He makes $10,000 a month.  He has a total of 4 properties including his primary.  Thank you in advance if anyone out there can help me.  By the way, I am looking for an LTV between 75%-85% if possible.