The short answer is ‘yes, you do’. The long answer is ‘it depends ………’

Private music lessons are usually expensive. But the expense is well justified because you get to learn from someone who is not only experienced in playing the instrument but also in teaching how to play it. With the money you pay, you get to buy the shortcuts that your mentor has learned from thousands of hours of practice. He or she knows what works and what doesn’t and therefore it saves hours of your practice time as you only get to learn what works as opposed to going through a trial and error process. Other than learning faster, learning under the guidance of a mentor means the chances are much higher that you will actually get to learn how to play the instrument and not quit after few months of trying. According to a study done by Fender guitars, around 90% of people quit playing guitar during their first year of learning. With an inspiring mentor, you are likely to be in the minority group of 10% and actually make it to the next level. 

But if budget is an issue and private lessons are difficult to afford, it is better to learn through alternative means instead of going to an unqualified guitar teacher who is willing to give lessons for a very low tuition fee. There is a plethora of tutorial videos on YouTube, short courses on Udemy and Coursera that you can try to resume the learning journey. The other alternative is to get few tips from friends or family members who play the guitar. 

So in a nutshell, if you can afford private lessons, go for it. You will get the worth of every penny spent on lessons and you will not regret it in the long run.  Otherwise, use the alternative sources of learning. If you are sincere, you can certainly learn how to play just watching YouTube videos. But with  the same level of dedication, you’ll go miles ahead working under the guidance of a mentor.