If you select a deep ITM (50% og share price), the time premium is quite low. Jan17 120 stripe TSLA is priced 121.25/124.25 (bid/ask) when SP is 236.61. This gives a premium of 3.14 (middle price selected). Also note that the time decay is not linear. It accelerates at the end, so by rolling out the options to jan18 (when bid/ask is reasonable), the actual time-cost is probably lower than the bid/ask-risk.
Using deep ITM leaps is probably cheeper than borrowing money to give a 2x gearing, and some of the bid/ask risk + time decay can be further reduced by selling shorter time, higher strike calls as "covered calls" on the leaps.
Edit: Example: buy a Jan17 120 strike call and selling a Jan16 300 strik call (diagonal call spread), is priced 111.70/115.05 right now when SP is 236.61. Break even Jan 15. 2016 is 233.31. If the SP is 300 at this time, the profit is 6621.80, with a ROI of 57.56%.