Old electrical wiring is something that I test if it looks dangerous. I am not an electrician and all electrical work should always to be performed by an electrician, so my job as an inspector is to note issues in the report for you the purchaser to act upon if you buy the house. Often old electric water heaters or evaporative air conditioners are disconnected or removed from the roofing space in older homes. In most of these houses the wiring has been correctly terminated or disconnected. I however still do find poorly insulated, cracked and exposed live wiring, or junction box's not covered from home DIY projects in quite a few houses. Accidentally touching any of these while crawling through the ceiling space can be hazardous. Electrical work when done by licensed tradesman is generally very tidy, with clips holding the wiring tightly back to the hanging beams and along rafters, additional wiring has been trimmed off when the cable run was installed. When wiring is seen coiled up you know that the work is sub standard or most likely it has been a DIY effort.