They offer the following list of things to sell.
Water magic services to diagnose and treat diseases.
This has startup time in the form of figuring out Amentan biology and calibrating their tools for it. They are confident that they can get it to work, since water magic works fine for other species, though when is another issue
Provided there aren't issues, it would take a week to a few weeks and they would need to scan people to get data for it. The scanning is noninvasive though for safety they would want stuff like tissue and fluid samples.
At highest throughput they would be able to treat a gross people in a week. They would be best placed to treating injuries which cannot be healed by Amentan medicine. They can do restorations of lost body parts (they can do up to "you got beheaded and we grow a new body for you"), deaging, restoration of fertility, cosmetic changes, sex changes, etc.
Wind magic and psion services for mental change and for treating mental illnesses.
This theoretically requires no startup time, but since mental issues are highly culturally dependent, they would want to study this at least somewhat before beginning. They are confident that this will work because their telepathy and mindreading works fine.
They can treat stuff like depression, anger issues, anxiety, attention deficit disorder, bipolar disorder, et cetera. They can also do more mundane things like "I want to develop a habit of X". It is possible they would be able to treat bad springs, but it seems like that is a physical as well as a mental issue. They are unwilling to perform value change treatment at this time, nor prisoners or those remanded to mental institutes involuntarily. Value change is stuff like "I don't love my spouse anymore and wish I did".
Wind magic can't do lasting magical effects. For something to stick, the application has to be either strong enough to affect nearby mental structures such that the mind is fixed into that new shape, or applied repeatedly. They greatly recommend the latter because it's more reliable and safer, but it's slower. How many times a patient needs to come in is very variable. For inpatient treatment, a week to a month is typical. For outpatient treatment twice a week, a month to a season.
Time in the zero-g rooms can be rented out.
Sex work! Also psionic sex work! You can do lots of cool things combining the two. Some people are good enough with their psionics to share a lot of their qualia so you can feel what the other person is feeling.
Also they are willing to act in porn and receive a portion of the profit.
Regrettably, a lot of their trinkets cannot be sold because they involve magic, and so would stop working (though not instantly) once they leave the hands of the Asteralians. Also, it doesn't seem like there are any fire or stone magic services that they can offer, only infrastructure, which would take too much time or would stop working/not work if there aren't Asteralians managing them.
How much would the Amentans value these?