I recommend the following basic tests:

Free Tests:
Waist-to-Height Ratio
Blood Pressure (free at many grocery stores)

Cheap Tests:
Fasting Blood Glucose 

Lab Tests:
Fasting Insulin
Hemoglobin A1c (HbA1c)
Triglycerides
HDL
Fasting Glucose

I recommend Walmart's Prime ReliOn--reliable & cheap.