Nowadays more and more hosts has some security against DDos. So before renting a host ask about DDos protection, there are also some scripts what you can run on your website during the attack, which make some protection. Also a good idea if you choose host which is specified for PTC sites and several big PTC hosted on them. Of course these hosts above not cost $4.00 monthly.

About enemies...some hackers did it for money, other black hats just for fun. Not mention that if your site become well known, and successfull I can garantee the there are a lot of jelous people will make steps against you.