Extraction of last back bottom tooth (not a wisdom tooth) and not replacing it

My back left last tooth on the bottom either needs a root canal (which I cannot afford; having been saving for months and still barely half way there) or can be extracted. I know that the top tooth would eventually start lowering itself and I would have to deal with that. Besides that, what issues may occur if i do not put anything in it's place? tried attached a picture but it would not accept the format

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