Hi Yeury! Happy new year and congrats on your purchase!
We have a MF here in RI as well. Did most of the work myself in most units, but am in the process of a more heavy reno on another one of the units that I am contracting. I do a lot PM work for my W2, so I have no issues managing multiple contractors schedules and timelines, but that's my experience.
I've gotten recommendations primarily via word of mouth mostly but also have done a decent bit of hiring through Thumbtack to be honest. I can send a few recos your way for sure if you'd like.
For the more costly/advanced/difficult work (electrical, major plumbing, complete flooring) I've signed agreements, but for the simple stuff it has been emails/texts/handshake agreements. Not the best methodology, but if I get burned for a few hundred bucks I can live with it.
Get a few quotes/bids before doing anything for sure, in my experience there haven't been any real drastic differences between the various bids (all within $500-$1000 or so of eachother)
Good luck! What area is your new purchase in?