A Theravada Buddhist lay attendant or steward is called a kappiyakāraka or Kappiya in short.
According to the PTS Pali-English dictionary entry on Kappiya:
Kappiyakāraka "one who makes it befitting," i. e. who by offering
anything to a Bhikkhu, makes it legally acceptable Vin i.206;
Basically, the lay attendant or steward, a kappiyakāraka, is the enabler who makes things allowable for monks.
"The Bhikkhus' Rules: A Guide for Laypeople" by Ven. Ariyesako provides info on lay attendants or stewards. Please search the page for "attendant" and "steward". Also please search Pli Tv Kd 6 for "kappiyakara".
The lay attendant is expected to receive and manage donations (money, robes, things, raw food ingredients, medicines etc.), buy things with donated money and distribute things to monks. The lay attendant can also cook food for monks (who are not allowed to cook), make fruits with seed allowable for monks and drive monks around in cars (since monks are generally not allowed to own or drive vehicles).
Both full monks (bhikkhu) and novice monks (samanera) are not allowed to handle money or make financial transactions. This has to be done by lay attendants. A novice monk cannot handle money because he observes the ten precepts.
I expect that a lay attendant must observe the five precepts, have taken the threefold refuge, be trustworthy, be well-versed with what is explained in "The Bhikkhus' Rules: A Guide for Laypeople" and have an abundant spirit of volunteerism.
An anagarika ("homeless one") is somewhere between a novice monk and a lay person. He is a lay person who observes the eight precepts. A person who wants to practise full time like a monk but does not want to observe all the monastic rules, may choose to become an anagarika.
The anagarika can handle money, so he can also act as a lay attendant (kappiyakāraka).
The Bodhinyana Monastery in Western Australia, which belongs to the Thai Forest Tradition, requires a person to be an anagarika for a certain duration of time before he is allowed to become a novice, and later a full-fledged monk.
According to this page, the duties and responsibilities of the anagarika at the Bodhinyana Monastery is described as follows:
The men with shaven heads and wearing white, while keeping the eight
precepts, are called Anagarikas. It is their intention to become a 10
precept novice monk in the near future.
There is quite a lot of work involved, supporting the monks and doing
various jobs around the monastery. This includes:
- Working in the kitchen – cooking, cleaning and washing up.
- Driving – there are many trips each week into Perth and the surrounding areas.
- Weeding, digging and gardening jobs.
- Construction of various projects.
- Sweeping around the monastery grounds and generally keeping the place tidy and presentable.
From the above, we can see that the anagarika is expected to cook or drive monks around, hence he could function as a lay attendant too.
Anagarikas at the Bodhinyana Monastery will also receive lessons in the Dhamma (in the form of Dhamma talks), Vinaya, Pali suttas and optionally, the Pali language.