would that void the current lease?

Due to item 1, adding an ADU can require years to start achieving any return (once the accumulated cash flow recovers the initial negative position).4) Adding an ADU is a slow process.

We started raising the rents on the 3 and 4 BR units until the rate of leasing slowed to a normal pace.Fast forward two years and we found ourselves with higher vacancy on those same units. 

Ironically the invested capital is often very similar for either. because your either investing capital in # of locations to scale, or investing capital in higher quality ie higher cost assets and operational items. 

You can get some estimates from contractors for what they charge for big ticket items like to renovate a bathroom, renovate a kitchen, replace the furnace, replace the roof, etc.All wholesale deals should have free and clear title and you should be able to see the sales agreement before submitting the earnest money deposit.

If you intend to vacate, the original lease agreement states you have to provide a 30 day written notice of your intent to vacate.

The AP has to be open, notorious and hostile...those terms have a legal meaning and essentially it is that you as the owner have been fully deprived of your right to the property.Absent those items above, it sounds like at best they have another legal right which is a "prescriptive easement".

Show the lease agreement, show his rent payment history, and show any written evidence from the tenant that he admits to being late/unpaid.

I could completely be misunderstanding the process, so thank you, in advance, for clarifying these items for me.

This way I get paid upfront for my work 1-2k plus I know I have another payday at some point in the future if the deal closes.The costs to fully develop a property and sell for near retail usually involves the costs below and takes 2-6 months or more in some cases, but the profits can be huge if you're working in markets where land costs are high:Title 200-400Legal 500-2000 depending on zoning issuesIf wetlands are present AND its a buffer zone project: 2000-5000Perc & septic design if needed 1500-3000Treescaping & cleanup for retail sale 500-1500Selling costs of 6%I tend to stay clear of properties that need more than the above expense items.