I joined a coaster through Gulfstream Shipping. I had no complaints about the crewing agency, as they handled everything promptly. They said the commission could be paid upon joining or even from the first salary.
I am currently working through Gulfstream Shipping. They are intermediaries who know little about the vessels and charge a large placement commission. The vessels are old and in poor condition, supplies are almost nonexistent, and when problems arise, the response is that I should solve them myself.
I worked through Gulfstream Shipping some time ago, when they had four vessels. It was acceptable as a starting point and helped me gain experience, but the pay was not very good. They have repeatedly offered me a return, but I regard them mainly as intermediaries.