Note Evaluation

[George Frye]

I am researching a note I came across. AT first it seems like a pretty standard note. It is a Mobile home with the lot for sale for 45000. The Owner received $20,000 down and carried a note for $25000. The interest rate is 8% for 45 months. 2 months have been paid on time. However the payment schedule is kind of weird. They pay $500.00 8 months out of the year and $1000.00 4 months out of the year. So How should I go about evaluating this note so I can either decide if I am going to purchase this one or pass it off to another buyer. Please help.