I wouldn't say its a negative connotation as much as a difficult road. First, it's extremely hard to type in a new airplane at a new company. Fire hose? Try two at once. And the FAA is notoriously hard on street captain type rides. I've heard bust rates in the 90 percentile for first attempt. Not a good thing to have on your record.
Then if "your buddy" passes training "he" will be at the bottom of a seniority list for a long, long time. That means reserve. And the FOs who are ahead of you will keep upgrading and bumping you back.
The negative connotation comes in because most of the companies who would hire a street captain are not the highest in repute. I mean Gulfstream? Not so good on a resume. And the pay is hardly worth it. Finally, lots of people see it as cheating rather than paying your dues. I mean you say you... uh "your buddy", got furloughed, but still, a lot of people see the street captain thing as trying to back door your way in.
But if you search, you can find lots on this topic on this website.