The big question for electric-car company Tesla (NASDAQ: TSLA) right now is whether it can become profitable in the second half of 2018. Losses have been mounting, and the company's negative free cash flow has been worsening.Last year, Tesla's total net loss was $2.2 billion. Even worse, its operating cash flow less capital expenditures -- or free cash flow -- was negative $3.5 billion. Kicking off 2018, Tesla's net loss was $785 million in its first quarter alone and its free cash flow during the period was negative $1.05 billion.Fortunately, Tesla CEO Elon Musk has said he expects the company to be both GAAP profitable and cash flow positive in both Q3 and Q4.