Looking to buy 8 properties which is a total of 18 units

[Brad Starks]

I am looking to buy 8 properties which have 18 units total.  Is this a good buy?  Please let me know what you think?  

$10,000 per month in rent

$650,000 land contract 15 years

tax & insurance  $2300 per month

payment for land contract $5,200 per month

management company $1000

What other questions should I ask the owner?

Thanks for your help!