This is an educated, upper class, Latin American family.So, should I insist on a co-sign or just go for it?

So I used my father as a co-signer.

I should also mention that a month ago a co-worker sold her home to a yellow letter investor..

I'm not sure on this but you might be able to do it if you had a co-signer (like parents or something).

It will be very difficult to obtain a loan for buying into a Co-op, I have a buddy who bought a co-op in Rogers Park awhile back few years ago and he said it took awhile but was able to get it done.

I did send them a polite message to try and remedy the situation with two options - either the son vacates or gets himself fully approved as a co-tenant.

Summary of stats:Real estate valuations: 880,000 (500k 2 Family 380k Primary)Mortgages: 666,000 (318k 2 family 353k Primary)LTV – 2 family is .63 Primary is .9225k cash availableCredit in the 700’sCurrently not set up as a CO.4500 in debt can and would be cleared prior to next purchaseThanks in advance, happy I found this community and look forward to contributing and learning all the same!

Although i had some rough financial times with work slowing down and issues at the house, I’ve had plans to sell it for roughly 2 years now, especially after I started talking to a co-worker that had about 10 rental units at the time.

Then the remaining $1735 should be split 50/50 with me, as if he was a co-partner in owning the house. 

A co-ownership agreement would lead to greater transparency between everyone (who does what, fees, who contributes what - labor, capital, etc.).