whymarywhy's journey

I recently had an interview for a job that I was really excited about, but I feel like I completely undervalued myself during the salary negotiation. I asked them to match my current pay at $22/hr, which includes health benefits, dental, vision, and 401k. However, I later realized that the job listing had a low-end salary of $51k a year, which is significantly higher than what I proposed. The owner mentioned they would be sending me an offer by Friday, and I can't shake the feeling that I messed up. I was so stunned during the interview because they seemed to really like me, even skipping a second interview and having the owner meet me personally. Now I'm in a dilemma. I want to work for this company, but I know I should have asked for more. I’m considering mentioning that if they could offer me at least the starting salary of $51k, it would really help me with my schooling and relocating to their area. But I'm worried about souring the relationship before I even get the offer. Should I wait for the offer to come in and then negotiate, or should I bring this up before they send it? I’m feeling pretty anxious about this whole situation.