You can put just about anything you want in an offer, as long as it's something legal. However, if you are competing with other buyers for the same property, "lowballing" AND adding a contingency may not be the best way to get an accepted latter. Better to just include the standard financing contingency -- that you must have approval for your loan -- if you plan to add a contingency. If you don't complete the course, you don't get the loan, so that cares care of the problem.
Having said that, I really recommend that you complete the course and approach sellers with a a pre-approval (also called a credit approval) letter. That shows that you are a serious buyer who can close as long ass the property meets the lender guidelines and apprises for at least the sales price.
It's the next best thing to having cash. Thanks you for writing and good luck with your home purchase.