@Adan Cordova,
The way I did it was did a walk through with my "compadre" who is also a contractor. We went through and wrote down everything that was needed to be updated on the home.
I start with major systems:
Roof- does it need to be replaced
Electrical- has the panel been updated and has the wiring been updated
HVAC- does it need to be installed or updated
Water heater- does it need to be replaced
Then we looked at the cosmetic and value add items
Does kitchen need to be updated
Do bathrooms need to be updated
painting interior and exterior
After walking through, he has been in the business so long that he gave me a cost for each job. The cost of a job is impacted by many things.
If you owner build and hire out it is less expensive then a contractor doing the whole job for you
If you get some paisas from home depot to do all the work it will be even cheaper.
He gave me ball park for all options. He did all my electrical because he was giving me the family price and he is also a licensed electrician.
from this walk through I was able to make a pretty good working budget.
I worked off of this budget but still went over due to things that came up.
I hoped this helped.