How many months before I buy a house should I start buying household items (furniture, kitchenware etc.)?  

Decide if you will be providing furniture for the bedrooms/separate dwelling units or not.7.

if you are planning to do the work yourself and can stand plaster dust destroying your electronics and furniture,horrendous paint odors you might be ok. the contractors doing the rehab will definitely not like it. rent a trailer with a bath and kitchenette and live in the driveway until completion. doing this will be better for everyone's sanity!

We gave them old furniture & appliances that others would throw to the curb.So if is just a 'business' would you evict & take the profit???

The investor and I used our own furniture to stage the property.

At that point we bowed out of the program.When the tenants moved out (with no written notice of course..and no rent for that month) they claimed no damages,  ignoring the 24 bags of garbage, the three broken appliances, the broken furniture and the unplugged but still half filled chest freezer (gag) of food they left behind (poor people tend to save EVERYTHING even broken stuff).The irony of these poor folks with their adult daughters who appeared to produce children with anyone they dated and no one seemed to question six grand children with six different last names is that mom and dad were supposedly very active in their church. 

If you are going to stage I'd imagine you'd like a place to store a majority of your furniture and accessories.

After removing all the trash, the house was so bad it needed to be demoed.And another hoarders house, after family took the valuables, and furniture people took the furniture, and scrap people took the metals, we still had THREE 40 yard dumpsters of trash.And at another place the outside looked fairly good, but inside the finished basement was submersed in 2 feet of water for 2 years, yuck!

One thing you have to realize , people will put down throw rugs , furniture , etc.

I also had purchased a foreclosed condo which happened to have a large number of pieces of new furniture in it, which helped me save on furnishing costs.