Doing It Yourself
Eavestrough cleaning is simple work at a dangerous height, and ladder falls from exactly this job are a well-documented category of serious injury.
Short answer
The risks are falls, overhead power lines, damage to the trough from leaning a ladder on it, and roof damage from walking on it. On a bungalow with good footing and a stable ladder it is reasonable work. On a two or three storey Toronto house, on a slope, or anywhere near a service drop, it is not.
The actual risks
Falls from a ladder, which is the main one and which happens when reaching sideways rather than moving the ladder.
Overhead service drops, because the electrical service enters most Toronto houses at the roof line near the eave, and a metal ladder near it is a serious hazard.
Leaning the ladder against the trough, which deforms it and is how a lot of sag and pull-away starts.
Walking on the roof to reach a trough, which damages shingles, particularly in cold weather.
Soft ground, which lets a ladder foot sink and shift mid-job.
And wasps and hornets, which nest under the eave and in the soffit and which are the reason more than one person has come off a ladder.
The service drop
Find where the overhead service enters the house before putting a ladder up, and stay well clear of it. The clearance is less than people expect on older Toronto housing, the insulation on an aged drop is not to be relied on, and this is not a risk worth taking to save a service call.
When it is reasonable to do yourself
A bungalow or a one-storey section, on firm level ground.
With a stable ladder at the right angle, tied or footed, and moved rather than leaned from.
With a standoff or stabilizer so the ladder bears on the fascia or the wall rather than the trough.
Clear of any overhead service.
With somebody else at home, which matters more than any equipment.
And in reasonable weather, with dry footing, which rules out most of the late-fall window when the job actually needs doing.
When to pay somebody
Two or three storeys, which is a great deal of Toronto housing.
Anywhere near the service drop.
A steep roof or difficult ground — a slope, a deck, a narrow side yard, a rear laneway.
A long run where the ladder would need moving a dozen times.
If you are not entirely comfortable on a ladder, which is a perfectly reasonable position.
And because somebody up there will also see the fascia, the slope, the hangers and the soffit condition, which is information worth having and which you do not get from the ground.
Common questions
Is cleaning my own eavestrough safe?
On a bungalow with good footing and a stable ladder, reasonably. On two or three storeys, no.
Can I lean the ladder on the trough?
No. It deforms it. Use a standoff so it bears on the fascia or the wall.
What is the hazard people forget?
The overhead electrical service drop at the roof line.