We are unlikely to disagree to a request for a goldfish or guide dog. In a non sharing house we are more likely to agree to pets.  I.e. a house for one.  In the unlikely event we agree to pets there is an administration charge of £50 to consider and agree to your request.  No charge for a guide dog.

We are normally unlikely to agree to other pets for for the following reasons:

At least 50% of times when we have agreed to pets we have regretted our decision. 
We consider each request based on anticipated risk and mobility.

The problems experienced to date have ranged from:

Damage caused by the pet - ruined furniture, urine stains on carpets and smells, fleas, (e.g. hamster ate curtain though cage on window sill) etc.

Other housemates initially agree, but later fall out over the pet and this has included:

A second housemate retorting, "you agreed to one housemate having a pet so I would like one too."  Other tenants later claim, "I did not realise the consequences of pets".
"I did not know I was allergic, now their pet has become more important than my heath!"

"I did not think the others would allow it to walk on kitchen work tops - it is unhygienic, I am leaving!"

Other housemates initially think, "how cute", until they endure the smell in the hot final months of the contract when exams are looming and nerves are strained. 

One housemate left (with his pet) at the start of term in a hot September when another tenant complained bitterly that flies were swarming around the droppings, the inseparable student and pet departed together, amidst great acrimony. 

Phobias (irrational fear of harmless thing) and realistic fear of certain pets are likely to put off specific prospective tenants from viewing during your occupation, e.g.:

Rodents, snakes, large spiders. 

Some claim they will keep the pet in an outbuilding and not in the house - but bring it in during the colder months which coincide with viewings.  Some turn the heating up to keep the pet warm to the discomfort and annoyance of other tenants.

Impressions and perceptions are important - viewers from November to January have stated they could not live with the smell – “do you have any other houses?”  It does not help to say the smell evaporates with the departure of the pet.  The first impression has already been made.

LINKS:

pethouseclub.com