https://www2.illinois.gov/…/construct_mainstreet.aspx (not sure they are HO scale – actually I don’t think they are… I think they may be 1/64th but am not sure about that… What’s cool is they are based on actual buildings… (using them that way on my slotcar layout) could probably be resized. Also not ho scale but 10 mm buildings are over at https://ttcombat.com/pages/dropzone-commander-buildings… – to resize those you basically print them at 184% in adobe pdf reader app… choose print, select poster and then chnage scale to 184%. Finally – http://www.haunteddimensions.raykeim.com/index301.html has a few famous mansions like the ones in a few scary movies. Just print these to card stock… You could theoretically scratch build em too, but that’ll be a lot more costly. Also check out papermau… no need to reinvent the wheel.