I'm thinking that a houseguest who stays on your couch should be something like hospes lectuli. But that sounds more like a guest invited by your couch, which is silly. In my non-expert understanding of how Latin normally works, this kind of construction should call for an adjective. But all I know is the noun lectulus. How could I make that into an adjective so that it clearly modifies hospes?
In your question you have used the genitive, and 'lecti' of a bed may be your best option. Or 'lectuli.'
It's almost impossible to find an adjective from any of the words for bed; and those two which can form adjectives imply the guest is sick or in child-birth. Lectus, torus, cubile, stratum (often in plural) or even clinus, tectus and grabatus.
contubernalis, a couch fellow.
sounded promising, but it's the (ten) men who shared a tent in the army.
In general, adjectives from nouns are difficult; it is much easier to form adjectives from verbs:
cubans: present participle of cubo: lie down,
Hospitality is best expressed by:
Hospitio aliquem excipere where 'aliquem' stands for any guest.