of course one could say, since the agent route is considered illegal by many, that Khun Ron proposed to do something illegal by going the agent route if you don't have the funds on your own. Yet, nowhere in the police order it's stated that it is forbidden to borrow the money you need in your Thai bank account
Khun Ron actually recommended the fully (!!) legal route to a 90-days Non-O visa and from there to the 1-year extension. If you want to find people promoting something illegal, go to those who have proposed to use an agent without having to show own funds
Philip Connor . . . it is rather the other way around: in order to apply for the "change of visa type" from a tourist visa to a "90-days Non-Imm-O retirement visa" on Immigration, a one-year lease if very helpful, because a rental contract is one of the requirements for this application (here, Chiang Mai immigration)
there might not be any agents in Supan Buri, because this is not a very touristic area or an area used by many Expats. I recommend you take accomodation in either Hua Hin, Pattaya, or Bangkok, and proceed from there. After you got issued your 1-year Extended Stay Permit, you can register your accomodation in Supan Buri and use their Immigration for all future extensions