
You can't purchase a well-fitting suit if you are unsure about your actual size. American designers and manufacturer each size to an exacting model, so a size 6 in one label could be a 4 or an 8 in another. Knowing your bust, waist, hip, inseam and sleeve length will help a salesperson fit you suitably.
A good pinstripe suit is a benefit, but you shouldn't need a loan to pay for it. The cost should be directly proportional to the suit's value. A classic, subtle cut in a good fabric that can be worn more than a few days a week with different accessories is worth paying more for than a flashy, trendy suit that you can only wear on sure occasions.