Hi
I'll make a stab at this one. Don't know anything about Philadelphia in particular but can speak from being a US citizen born and raised. We enjoy many levels of taxation in this country

. Property is taxed at the local level or should I say town or city level. Taxes are based on valuation but there are many factors involved in the calculation. If you're trying to determine the value of assets of your ancestors then I would imagine armed with a street address there could be a way of tracking down a particular property at a particular point in time. Property taxes are an annual event but these records would only be held at the town or city level. Don't forget that census returns contain info as to whether the individual owned or rented their premises. This question appears on each census from 1900 through 1930. This info might help you determine if there would be property tax records in their name. For example....I live in Maine. My town holds a "town meeting" once a year and votes on various articles that will determine how much the town will pay for services (rubbish removal, road maintenance, fire protection, etc etc) and operating costs for the coming year. Once this budget is approved then the tax rate gets set to make sure enough income is coming in to pay for it all. The real estate is appraised and re-evaluated at regular intervals to coincide with current market values. This makes us think we have a say in how much our taxes will be each year

Another possibility is to track down probate records (deeds) which will record the transference of ownership of real estate (land and buildings). These court records are held at the county level in my part of the country. Not sure if that is countrywide. Some areas even have online access to records. The trick is to identify the location of the county courthouse and to also make sure the county borders haven't changed over the years so that the particular citiy or town your looking for is in the county that you're looking in.
I guess I'd go looking for the equivalent of the office of the tax collector for the city of Philadelphia and see what comes up. There's usually no shortage of personnel in these areas....someone out there has got to have an email contact listed online

Hope this helps

Jean