I stumbled on this thread when searching for the location of the poorhouse in Busby for my own reasons, so thought I'd share my findings in case it's useful to anyone else, as there is very limited information on this.
The annual report for Local Government Board for Scotland 1902/3 has the only mention that I could see, which stated:
"In consequence of the inability of the Parish Council of Paisley
longer to retain in their Poorhouse paupers from other parishes
boarded under the 65th Section of the Statute, the Parish Councils
of Eastwood, Rutherglen, Neilston, and Lochwinnoch combined for
the purpose of obtaining temporary Poorhouse accommodation. A
disused factory at Busby was acquired for this purpose, and after
having undergone the alterations necessary was sanctioned by us as
a temporary Poorhouse to accommodate for a limited period a
number of inmates not exceeding 116. On a further alteration
having been made on the building — the effect of which was to
provide another dormitory — we sanctioned the occupation of the
house by a number of inmates not exceeding 140."
So it appears the poorhouse was a temporary measure established some time around 1902 to accommodate the overflow from the Paisley poorhouse, specifically that from the Parish Councils of Eastwood, Rutherglen, Neilston, and Lochwinnoch. It occupied a disused factory somewhere in Busby and housed 116 people, increasing to 140 when subsequently altered/renovated.
It seems likely that the 'disused factory' referred to is within the Busby Print Works, which sits alongside the railway and is depicted on the 1897 OS map as within use, but on the 1913 OS map as 'disused' (attached). Since it's not labelled on the 1913 map, I assume the temporary poorhouse here was no longer in use by this point and the Renfrewshire Combination poorhouse constructed in 1906 probably absorbed the residents. In any case, if the factory building used as the temporary poorhouse was located within Busby Print Works then it no longer survives.