I'm replacing all the windows in a manufactured home (about 16 I think) and some of them are large picture windows for about $4,300.For window panes (like fixing broken seals or a single cracked pane), try Diamond Glass.

But bringing up a hinge on the electric panel is absurd.How do I approach this request?

Although they have been able to pay rent so far, I know that it is an incredible strain to do so and that eventually it will become impossible for them to continue to make those payments.  

When you put your assignment fee on top, it strains the existing economics, so you have to get a price lower than what it's worth to handle the fee.Most people find assignment buyers by posting on the MHU forum and saying that they have an assignment for sale.

In general it best not to rent to family as it can put unnecessary strain on relationships.

The panel is only around $2k worth, I wouldn't count it.

Maybe not the top of the line since they are real expensive,,,but one that is efficent enough to use 2 small pvc pipes to the outside walls to vent /intake.I grant my house is small,800 square feet, new double pane replacement windows and I set it at 65*(makes alot of dif) but the coldest month of all should have been last month,,,had a few 20 belows in there,,,and gas bill was 106 bucks for 32 days.

Palmdale/Lancaster doesn't do it for me for the reasons I stated, and as far as picking through looking for a renter's pool....I figure why strain so hard to find good renters when other places have more obvious, bigger pools of them?

The box sits on the wall, the wires run through the wall, if a tenant starts worrying about radiation from the electrical panel I would tell them they might want to think about finding another place to live. 

Improvements:  ADDING new features or upgrading an existing feature.eg:  Old window may be a single pane casement style (crank to open) and the upgrade may be to a dual or triple pane, eGlass with Argon fill replacement.That's an improvement, a capital expenditure and amortized.