You can do a half-marathon without training

What do you think? Is a untrained person able to finish a half-marathon?
How Hard Can It Be to run a half-marathon without any training? - YouTube

So if you can do a half-marathon without any training, then a marathon with a little training is even not a problem.
Well may be the broom car might be the main problem and your health and may be you fail to enjoy the run and life after the marathon.