Roofing contractor agreement and advise

[Sal Flores]

Hello BP'ers

I am almost to start rehabbing a small old duplex, is a 1920's  property 1,940 sq. ft, the existing roof it has 3 layers,

One of the contractors gave a quote he said, possible some of the wood can be saved and might just reinforce with some supports but will be known once remove the layers, that does not give a lot of confidence, because 2 previous high level specialized contractors said the wood must be replaced as well. but they stratospherically expensive over 20K

Does any one knows if per code in el Paso TX needs to have replaced all the wood?

Does any terms I should not miss on the agreement? any template recommendations?

Lately, any roofing company in El Paso that anyone can recommend

Thanks in advance

Sal