I've never heard of an ESOPP. I know of an ESPP (Employee Stock Purchase Plan) and an ESOP (Employee Stock Ownership Plan), and employee stock options. But maybe your company just calls one of these by a different name.
This sounds mostly like an ESPP, but in the ones I've always been in, I contribute the 10% out of each paycheck during the 6 month (or whatever time) period. I could pull it all out before the 6 month period, but it really makes no sense because I get a discount on the lower of the beginning or end stock price. I don't have a choice on when it is bought, it happens at the end of the 6 month period.
If yours is really an ESPP, you are going to be taxed on the discount as ordinary income. Any difference in the actual sale price from the offering price will be a short term gain or loss. It you can hold it longer--two years after the start of the offering period in your case--the ordinary income you have to report could be lower, and the rest is a long term gain (or loss).
If you're getting a discount plus the stock has gone up a lot since the beginning of the period, it's a no brainer to buy the stock even if you have to sell it right away in an unfavorable tax situation. You'll still make out well.
If you really have a choice on when to buy it, then the rules sound different from an ESPP so I can't give advice on something I don't understand. Maybe there are different variations on an ESPP that I've just never seen.
Guide to Compensation in Stock and Options
should cover all of the cases, and if it differs from what I've said, believe Fairmark because it's easy for me to explain this incorrectly.