First up, what do you want in a dog? What qualities? What don't you want and are undesirable train for you? Theres over 400 breeds of dog, that's without all the 'designer' named ones around now, so you really need to help narrow down your search or you'll be there a very, very long time! Write down some question and and answer them truthfully, things like
Light, moderate or intense exercise?
Heavy or light shredder?
Calm and laid back, or bouncy and active?
Good with other people/kids/dogs/animals?
Coat type?
Low, moderate or high grooming?
Activity level?
Trainability?
What do I want a dog for?
Cost?(big dogs cost more food wise, meds wise, even accessory wise)
Pedigree, cross or mongrel?
Size?
Space you have?
Health?
If you answer these truthfully, you will start to pick out certain traits, behaviours, appearance and personality that you like and equally those you don't, and you can start to build up a list of breeds to look up in more detail.
The basic cost of a dog is:
The dog itself - varies between free to good home and over a thousand for certain breeds/ top pedigrees
Vet fees. - a puppy needs two lots of inoculations, one at 6-9weeks, one at 10-12weeks. This is then followed up a booster vaccine each year. Spot on flea& tick treatment is given monthly, and worming tablets every two months approx. These costs are for routine treatments without any unexpected bills on top.
Neutering - optional but usually worthwhile doing.
Insurance - again optional, judge if you think its worth it depending on where you live. I don't insure because I live out in the sticks where its quiet and prefer to save a bit aside each month or whatever in a separate vet fund. If you never claim the insurance, just think how much money you've given for nothing

. On top of that, some are a complete rip off, not covering the very thing they need to be, not covering certain conditions/ breeds/ ages, not insuring a dog over 9 when they most likely will need it and so on. Read the small print very, very carefully.
Food - the bigger the dog the more it eats. Varies in price, but you should really opt to give the best you can, if you put rubbish in you get rubbish out, skimping on the food could cost you heavily in the vets.
Dog walker/ sitter - optional, but if its going to be in the house alone a lot of the time, its advisable.
Accessories/ essentials - food & water bowls, lead, collar, ID tag, toys, chews, treats, bed, crate (very useful to have), brush/ comb (depending on breed). All mounts up and needs replacing , some fairly often.
Grooming - depending what breed you go for, some need 6-8 weekly sessions at a groomers to keep the coat as it should be. These aren't cheap and quickly mount up!
Hope this helps gives you some idea of what to expect and need to think about

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