Most mobile parks do not come with land ownership. You would rent the land and buy the home. If you are going to buy a piece of land and place a mobile home on it, that's a different story. You would need to get local government approvals to do so. Keep in mind that the plot of land may have no improvements like sewage system, electric, gas, water to run to your mobile home and you would be financially responsible for getting approvals to install them, then paying the bill to put them in. On top of that, Mobile homes cannot be financed by a traditional mortgage, you'd need cash or a personal loan.
I think if you are pre-approved for 100k, you probably have more options than you realize in Philadelphia. I'd be happy to send you via email some available listings in Phila, just send me an email (below) and I'll return some listings.
Barbara Smith ABR, GRI
PA & NJ LIcensed Realtor