(taxpayer cannot reduce Schedule C gross receipts by cost-of-goods-sold due to lack of evidence as to how amounts actually used, or deduct like amount as a bad debt; taxpayer was investing in friend's start-up business of producing fly fishing "de-hookers" and "de-flyers"; parties agreed to treat investments as loans; no loan documents prepared, no promissory notes issued, no repayment schedule, no maturity date and no interest rate specified - it was merely hoped that repayment would occur from future business profits).