Home Price Prediction in Python: "invalid type promotion" - Error in Code

Hi everyone,

I am working on a project for prediction of home price trends on the national level for US. For some odd reason, my code is giving the error “invalid type promotion” when I run the linear regression. It is a multiple linear regression. I am using sklearn.

y variable is the Home Price Index
x includes multiple variables.

My code can be seen here: https://repl.it/@agarwalarti/BluevioletSlategreyPyramid

Could anyone please check my code & tell me what I am doing wrong?