I need a letter from a lawyer to someone who is trying to avoid the work

I need a letter from a lawyer to someone who is trying to avoid the work they were hired to do and suggest to him a lawsuit is coming if he doesn't complete the job as our initial agreement describes, including making sure that the tanent he has been managing the whole year (and getting his 8% managing fee from me for it every month) will paid her bills in full before leaving the house, for example. and also doing an inspection throughout the house on the 31 Aug (being her last day as my renter) and all other duties as mentioned in our initial managing agreement 2-3 years ago. I wrote to him that I want to take over the managing when the tenant moves out and he replied he is done working for me at this point which is not OK with me. I wrote back to him but he is ignoring me.