@Keith AnnisI'm not an attorney, but I don't think you need to prove anything to impose a fee that is a legitimate provision in your lease.I think it would be on the tenant to challenge the validity of it in court as a defense to the eviction you file for nonpayment of the fee, and the judge would then make a judgement based on both sides of the story (your explanation as to why you believed it to be occurring, and the tenant's explanation that it was not).

We have had a lot of rain recently but it has been 24 hours and I would expect it to have dried up by now.

If, upon obtaining a judgement in an unlawful detainer, the tenant does not vacate the premises, follow the law and have the sheriff assist them in leaving.If there is more to the story, do tell please. 

Maybe the guy is the Rain Man of auto F&I, but likely not, but hey... modeling numbers if fun sometimes, so F it... 

One of the biggest things I would do is sign outdoors, weather permitting (might be difficult if it's raining, with paper documents and all).

When it rains here, and it rains often, getting in and out of such a property would be difficult.

Give the tenant written notice that you will be filing eviction and seeking a judgement as soon as the law allows.

I would not try to do eviction myself, there are so many things that could go wrong and you'll have to restart this process again (in the best case) or will have to pay fines (in a worse case).Total eviction cost depends on many factors, e.g. if you need to go to the court or tenant settles, default judgement vs hearing, etc.

She may have to risk you filing a judgement.

@Kevin Stringari I have listened to interviews with one of the owners of those security deposit insurance companies and most of the time they will not pay out a claim unless you have a monetary judgement.