"He seldom sleeps here."

Translation: Tady spí zřídka.

[NinaOBel]

Spí tady zrídka - what is wrong

[Herman671749]

"On zřídka tady spí" couldn't be valid? Word order in Czech is more flexible than in English, for instance.

[endless_sleeper]

It doesn't sound very natural, to be honest. You don't use personal pronouns in Czech that much, so I would drop the on Also, keep in mind that you usually place the information you want to stress at the end of the sentence.

Zřídka tady spí. = 'He rarely SLEEPS here.'

Tady spí zřídka. = 'He RARELY sleeps here.