Reneging several months after accepting an offer?

Hey guys, I have an offer on the table right now. It is with a company that is pretty decent, but I'd like to continue recruiting for better jobs. However, I only have a week to decide if I want this job (and I don't know if I will land a better opportunity)

Would it be alright if I accepted this job for now, but reneged possibly in April or so if I get a better job? I was thinking I'd say something along the lines of my parent is sick and I need to be back home to take care of them (they're in a different city). Or if you guys have any suggestions for better ways to renege, I'd love to hear it.

Would love to hear your thoughts on this