Welcome to the forum! You'll find a wealth of information here with many members who have done the Fairfield or other half scale projects.
I'm currently towards the end of my first build - half scale Fairfield. I've given myself a christmas deadline! I've stopped and started. Gotten side tracked by making furniture and other bits and pieces. Ummmed and Arhhhhed. And I'm now up to tackling the roof! I've kept the same layout but made many alterations.
Because it's a "three dimensional" dollhouse (part of it's appeal & charm) I think it can become difficult to get into spaces to wall paper, lay the flooring, add skirting boards and run the wiring for lights once the next floor has gone on. So forward planning your wall paper, flooring and lighting layout is a must.
To be honest it's very achievable for a first build but it is complex and has taken me a long time to complete. We would call it a 'baptism by fire' here in Australia : - ) I would recommend starting by building the base and then dry fitting (slotting them in with no glue but using tape if necessary to hold them together) all the walls. This way your can start cutting out new doorways and windows, covering in old ones, moving/removing/adding walls, and changing the stair configuration. I achieve the cutting with a craft knife, a small hobby saw and a bit of patients, time and some muscle!
Good luck! Looking forward to hearing about what you decide!