Tenant Failed to Pay Sewer Fee to City, accumulated $20k in bill that we had to pay

[Tom Shi]

A thorny problem: 

My relative has been renting out a commercial property to a tenant for some years. The signed lease states that tenant is responsible for all utilities including sewer fee.  Unbeknownist to my relative, the tenant has failed to pay the sewer fee to the city for a number of years, finally accumulating a bill of >$20k including fines.  My relative was finally notified of the situation earlier this year.  Over the last few months, he tried to talk to the tenant about the situation and urged her to pay the bill but was met with stalling and lies (unfortunately nothing in writing, emails or texts, just phone calls).  The city set a deadline to pay the bill or the owner of the property would face special tax assessment, so my relative felt he had no option but to pay the bill himself first.  

My relatives would like to serve the tenant with notice of termination for cause due to breach of the lease (failure to pay utilities). In the termination form, my relative wrote that the tenant has the right cure the violation by paying back the money my relative paid the city.  

I feel a lot of things could go wrong in this situation and have urged my relative to seek proper legal counsel.  He is reluctant due to past experience with the cost of such things.  He was going to just run it through one of those online $50 a pop legal questions website.  I am not sure if that's the greatest idea.  If any of you have recommendation a decent tenant law lawyer for landlords in the Portland OR, please share.  

I also feel that this tenant has exhibited many untrustworthy signs and it's best just to cut ties to protect oneself.  What if the tenant agree to the "cure" by just proposing to pay extra $100 a months for years until the full amount? I doubt my relative can stipulate a lump-sum payment? Then my relative is stuck with this very untrustworthy individual for long term.  My relative prefer to get this tenant out due to this and past behaviors but also has some ambivalence as he feel this particularly property is hard to rent out; this tenant despite some periodic delays, has not been past due in rent all this time. 

My relative also is planning to meet with this tenant today to serve this termination notice. I urged him to hold off until he has a clearer sense of all the legal ramifications.

I am kind at a loss at what's the best course here.   Any advice, past experience with similar issues would be appreciated.