Do the tenants have a lease? Are there late fees? Are they tenants paying the late fees? The LL can serve a Notice to Quit for habital late payment of rent. Then they can be evicted. However, if your parents are having a hard time making ends meet this may not be the solution as your parents would incurr costs to re-rent the apt etc. The better solution is that when the lease ends to add late fees as "additional rent." If the lease does NOT have those words you cannot collect a late fee. Also make sure that the tenant's security deposit is in a separate account and the tenant receives proper notification of where it was deposited or the tenant can use it as rent.
Habitual late payment of rent is a cause to evict under the anti eviction act. There is a procedure to follow as outlined in the act. If you would like a free consult, call me at 908 391 5399
As my colleagues have noted, not paying rent on time can be good cause to evict under the Anti-Eviction Act. Your parents' situation is difficult, considering they are putting themselves out of pocket in the short term to ensure the tenant pays rent on time. If this persists, your tenant may say the conduct was ratified and acquiesced-to by your parents, and has now changed the lease to that effect (I wouldn't want to make this argument in court, but it's a legitimate argument that won't get you laughed out of the court room by the judge.)
On the other hand, evicting tenants will mean your parents will be forced to dip into their pockets to cover expenses until a new tenant arrives...and that might take a month or several months. It's a lose-lose situation.
That being said, and with the understanding that I do not know your family's specific situation, my feeling is that your parents are losing money no matter what they do. However, if they remove the non-paying tenant, they can get a tenant in there who will honor their obligations properly.
The foregoing is not legal advice, and nothing in the foregoing shall be deemed to create an attorney client relationship. If you feel you need to speak with an attorney regarding your issue, it is recommended that you contact an attorney with expertise in your area of inquiry. The information related above is purely for informational purposes, and should not be acted upon without speaking with qualified counsel familiar with you specific situation and the laws related thereto.