Sounds like you might be cash-limited. I know the feeling - lost $26K selling a house, living on just my own income now, etc. And unfortunately, I also have the photo bug, although I don't claim to be good at it. I say "unfortunately" because that can quickly become one of the more expensive aspects of diving. So, stick with a cheap camera for now and put the bulk of your money into at least one decent strobe. You'll be able to keep the strobe later when you upgrade cameras.
As for diving itself, you don't say where you're from, but anywhere you can shore dive keeps the costs low, and for other dives see what kind of local groups are available to get group discounts. Even though I live in Florida, I'm in the central part and all the good reefs are down south, so I find the larger expense is travel and lodging - try to minimize that however possible, so that every dollar you spend is on diving and not just having a bed for the night. Once you've got all your own gear (much of which you can get used and save $$$), these travel and boat fees will be your main costs; tanks fills are the cheapest aspect.
Oh, one more thing: ditch the dog and upgrade to a cat. Preferably indoor-outdoor with cat flaps. No litter box to worry about and a big pile of food and automatic waterer, cat's good on her own for a long weekend off diving; independent, self-cleaning, largely self-maintaining, and nowhere near as needy or fawning. Far superior to a girlfriend/spouse/live-in and only slightly more upkeep than a throw pillow. Then again, I'm a cat person and intensely dislike dogs, can you tell?
