
Manager on a phone interview said I can expect to work 50-60 hours per week. Do you think that's reasonable...
Would you consider this a red flag for a salary position? The interview is for a Technical Support position with a national telecommunication provider. I know that I need a job and all but I have a new family that I’d also like to spend some time with eventually.

FYI: I have never worked less than that and as an entrepreneur I think that would be a wonderful break to only work 50 hours. But- only u can decide what's right for you. There's no wrong answer and it's nice that this employer is not misrepresenting expectations. Just be true to yourself....

Reasonable based on what? If this is a salaried job and everyone on salary is based on 40 hrs a week then this sucks. if overtime is paid for hours above 40 hrs then it is up to you if you can deal with it. If asked to work these hours without overtime check your state labor board because this practice is now illegal in many states. Welcome to slavery in the Brave New GOP Work World.

Isn't that the normal work week now?? Just make sure the compensation is right and you will enjoy the work.

That is overtime and excessive it is important to have a work life balance. I have worked every weekend Fridays through Sundays for two years and you miss out on a lot like your life. You have to weigh the benefits. Is the money a good salary then I say go for it. In my case the salary was not worth my personal sacrifice.
If it is Microsoft or another high tech giant with similar performance expectations, then it is definitely the norm. Whether or not it is reasonable depends on the type of work, the business group, and whether or not the leadership there respects that demand, and is capable of rewarding your performance commensurate to what they consider to be "baseline" expectations. Remember that, although 50-60 hrs/week is not normal for everyone, a lot of people wouldn't blink at this, especially if they have been at a high performance expectation company before.
If this is a concern for you, I would be open and honest with them about this in your next interview. There may be very specific reasons that they expect a 50-60-hour workweek from their employees, such as time-zone hand-offs or an abundance of critical work, and they may have an excellent reward system and/or work/life balance (W/LB) policy in place to ensure healthy, happy teams. If your interviewer works for a company that believes in W/LB, they will appreciate the question and think it is smart that you asked about this in a professional way. If they don't seem to have a good, ready answer for this, or it seems awkward that you asked, this could be an indicator that their performance expectations are inflated without rationale, and not balanced by appreciation, a good reward system, or other plans to keep their people happy.
Let them know how this compares to your experiences, how you have employed time management to ensure high performance in the past, and ask them to talk about the work/life balance practices at the company. Don't forget that you are interviewing them, too, and if they have performance expectations that you don't agree with or are uncomfortable with, then it might not be a good fit for either of you, and you can do better. :)