This is a generalisation, but from my experience - you may need bigger houses to make it work. Accountants, doctors surgeries etc want more than just a small 3 bedroom house they can convert to offices, so with a small house and reno. you'll only be appealing to a one man show.
I've seen it done with a few here at Norwood, but these are all bigger houses, eg. the last one had 8 individual rooms, plus a living area, cellar and a kitchen area. So that's potentially 8 offices, a board room, records space and staff room. The houses that weren't big enough had additions made to the buildings. Remember that you'd probably need one room alone just as a reception/waiting area - in a 3br house, this will take away say 25% of your space before you even create the professional rooms.
For a smaller tenant it may work, but then that will go with a smaller rent and relatively higher risk of a less secure tenant if it's just a one professional person operation. Probably not hugely better than a residential property, and with the less attractive financing options.
My accountant's firm works out of these sorts of premises, but they're a relatively big firm, and the last few years have still been running out of space despite owning two adjoining houses and from memory leasing a third.
You'd also have to comply with local council regulations including changing the zoning which can involve community consultation (ie. the nimby's next door), car parking areas which would likely entail you bitumising (sic?) the entire backyard and driveway(s), widening slipway into said driveway from the road. During this time (the example mentioned above took about 12 months for approvals and reno's) the property will be sapping a lot of extra cash from you without any tenants, and God forbid the council wants to play funny buggers and stalls you along the way (surely council wouldn't do that?!
). Just some other issues to be mindful of.
