It's a good idea!
cons: depending on how you buy your BTC, the current minimum tx fee will be the downside
it would cost you (or seller) significantly high when dealing with low amount transaction
if you can find a way to reduce the fee close to negligible, it would be perfect
Atm I just registered on Coinbase and waiting for verification from there, I thought of buying on monthly basis. Is it a good idea?
Being the investment expert which I'm not

I'm going to agree with those suggesting diversification. But definitely not making a loan to make an investment. If I had that kind of money I would be looking into storing some on a regular basis at FreeBitco.in where I can earn some interest [in addition to where ever you're planning to store your bitcoins].