I've fought for lower taxes, proven that they're too high, and was still denied a decrease.

Asking a realtor would help yes (whether it would change your price point), what the neighbors have helps yes, the cost of running the gas pipe yes (19k is huge but it may decrease your sell price if the area is conducive to gas and you have oil), knowing where that tank is at--if it's underground you may need to spend another 1,200-1,500 for an inspection of the soil because it can be a nightmare if there is seepage (bearing in mind that once this happens you now are responsible for any contamination because you documented it)--all of these responses are hitting on the head what Sharon said.

I would not decrease the rent for the feline decrease because they chose to give the cat away.

The less people there are, the smaller the demand, thus decreasing the size of a given market, this includes real estate. 

@Tom MoleI live in Sherman Oaks Studio City and I agree with you you need to think creatively in Los AngelesFind a problem and offer a solution that's where you going to get the valueOn small apartments or 6 to 8 to 10 units find a mom-and-pop landlord that is pulling their hair outYou can take a look at master lease options which you leased the property on the master lease, and have an option to buy the property based on the low noi or net operating incomeI would use private money to turn the property around and raise rents and increase services and decrease costsApartment accounting is a little confusing and I do enjoy @anthony chara s training on apartments@Anthony CharaIt's online it's not that expensiveIf you're in LA I would not try to do single-family house Buy and hold investingGood luck!

Just to be clear cost seg does not create more depreciation, rather it front loads a portion of the depreciation resulting in a much larger deduction now with a decreased deduction later.

Your goal over the next 24 months would be to increase the value of the property by raising rents and decreasing costs to improve the NOI.

To your point on the nicer neighborhoods, the coastal cities (i.e. currently both high priced and high rents) here in San Diego will experience decreased demand the most on the next market correction (I would assume the same in OC).

In terms of a percentage, how much would the noise decrease the value of the home when compared to a similar house which is not next to a major source of noise pollution? 

I could purchase this property and start charging for gas and electrick and that would decrease expenses by about $550/moI wish I could figure out how to attach a link to this post of my analysis on the Bigger Pockets rental calculator.