A 35i is always going to cost you money no matter how good the maintenance history is, I've owned by 2006 e92 since 2011 @ 52,000 miles, has now done 126,000 only 'common' issue it hasn't had is the injectors, still on original index 1. Then there's tyres & general servicing & maintaince & of course mods
Mrs Chappers used my 35i as a dd doing around 70 miles a day until 2015 & it was quite expensive for me to run as daily for her. It now only gets used by me a couple of times on weekends when the weather's nice
maybe have a read of the 'how much has your 335i cost this month' thread on the UK technical forum for an idea of running costs.
If you're just planning on running it for 6 months or a year you may get lucky & nothing breaks...or at least nothing to expensive..but if you are going to keep it long term then you will need deep pockets