probably been asked before but...

Yeah your friend was right. It is what it is. You have to be in something to be able to go out and know people. Unfortunately.

It doesn't have to be greek life but you really need to be part of something when it comes to going out. This could be a sport (club sports as well) or a club on campus. Having that group is super important but not hard to get into if you make the effort to try. Greek life doesn't just party with greek life, sports don't just party with sports... you just need to be in SOMETHING

When does greek life recruitment start and is it difficult?

Recruitment starts in the spring and this is the only time any of the nationals partake in recruitment. However there is fall recruitment but you must be at least a sophomore to do it and it includes almost all the locals except Ago. The only sorority at the moment that isn't taking an pledge classes is AOPi due to them being kicked off campus and ineligible until 2020.
Recruitment is not difficult per se but there are some sororities that are more difficult to get into than others. Also a lot of sororities begin rushing the girls they are interested in taking the semester before formal recruitment begins. Getting invited out with a sorority doesn't necessarily mean anything, but it is a good indication of things.
There are many unique sororities on campus and you should look into all of them as they all have something different and special to offer. You could probably categorize the sororities on campus by terms of personality, so if you vibe with a few girls in one sorority you might get the feeling for it as a whole. Round robin is a great event that happens during every formal recruitment season and you can check out each sorority and what they stand for. Hope this helps

The reason you didn't see greek letters on houses is because there is a town law that outlaws them

I think its actually because most greek organizations still rent their houses and the landlords don't allow it. AGO and Phigs own their houses so they can put letters on them.

Most orgs can't put their letters on their houses because they don't own it. Only a few older orgs own it like Phigs, DK, AGO, etc.

Most frats are also off campus, whereas other schools keep frats on campus. Most are on Orchard Street, but some like MAC, Theta Chi, Phigs, and DK are on other streets. Makes them less popular, but they have better houses.