There is not enough information in your post to comment on who, if anyone, is liable for the damages that you mention. Thus, I express no view on that. Your friends should retain independent counsel.
Although I can't comment on your specific situation, I can make some general comments about residential tenancy fires. The first thing to understand is that the law does not provide a cause of action for all damages. Just because somebody has suffered damages, it doesn't necessarily mean that anybody can be sued for those damages. In order to recover damages from the defendant, the plaintiff has to establish a claim known to law. In the case of a fire in the residential tenancy context, the theory most likely to be in play is negligence.
In Florida, a plaintiff can recover damages for negligence if he or she can establish breach by the defendant of a duty owed to the plaintiff, which breach caused injury resulting in damages to the plaintiff. Delgado v. Laundromax, 65 So 3d 1087, 1089 (FL 3d DCA 2011) (citations omitted). A tenant has a duty "not [to] destroy, deface, damage, [or] impair ... any part of the premises ... belonging to the landlord". FL Stat § 83.52(6). However, "the tenant is not an insurer" and is not necessarily liable for all damages occurring to the property. Kirkpatrick v. Reese, 240 SW 2d 1, 2 (AK Sup Ct 1951), cited with approval in Page v. Scott, 567 SW 2d 101, 103 (AK Sup Ct 1978), cited with seeming approval in Rausch v. Allstate Ins Co, 882 A. 2d 801, 813 (MD Ct App 2005), cited with approval in Lloyds v. Cape Publications, 63 So 3d 892, 895 (FL 5d DCA 2011). Indeed, "[m]ost fires originating in buildings are undoubtedly due to negligence in the construction, or to a want of repair, or to the bad condition of the building, chimneys, or heating apparatus, or to negligence in the management of the building or of the fires in it; and to require the occupants at their peril always to adopt all improvements which are practicable, and to take all precautions which science can suggest to prevent fires, or the spread of fires, would be intolerable". Kirkpatrick, 240 SW 2d at 2 (quoting Lothrop v. Thayer, 138 Mass 466). In order for the landlord to hold the tenant liable under a theory of negligence, the landlord would likely have to show that the fire would have been avoided if the tenant had "exercise[d] reasonable care to guard the premises against injury". Id (citing United States v. Bostwick, 94 US 53 (1876)).
A contract between the landlord and tenant can possibly alter the principles above, subject to the fact that "[a] provision in a rental agreement is void and unenforceable to the extent that it ... [p]urports to limit or preclude any liability of the landlord to the tenant or of the tenant to the landlord, arising under law". FL Stat § 83.47(1)(b).
I express no view on whether anybody is liable to anybody else in your specific fact pattern. Your friends are involved in a serious matter and they should retain counsel.
