Is it a good idea to sell older an home+ buy expensive new home?

[Mary Jay]

Do you guys think its a good idea to sell a 100 year old home, because its old, so I am worried about cap ex... 

The house is paid off, brings 650$ per month. I can sell it for 100K and buy a newer home for 300K but will have to put a mortgage on it for 20-30 years. It might cash flow, like $50-100 per month if I am lucky... 

What is your opinion?