I preached in “The Hands-Off Investor”, as well as on stage every year in my presentations at BPCON, that one of the strongest forms of “skin in the game” is “does the sponsor have a brand to protect?”  

Unfortunately, I dont think I can barge into their unit without them present.

When you find out the present zoning of the property, the future land use and the local agencies comprehensive plan for how they see the area being developed (all can be done at the local planning office) you will have a much better idea of what you have just bought.If the land could in any way be developed into something more than single family residential lots, i.e. if there is any multi-family or commercial component than I would advise you to hire someone qualified to help you with the site planning of the development.

One reason could be that not all appraisers consider basement space to be "general living area" (GLA), regardless of the building codes.To overcome this barrier, you can:Provide Documentation: Present the city’s approval for the egress window and any other relevant permits or certificates that show the space was done according to code.

Self defense training, situational awareness, pepper spray and de-escalation are all good.

I want to approach the seller on a seller financing opportunity but don’t know much about it, and don’t know how to present to seller.

Yes to everything @Nicholas L. said and also know your financial situation and have your finances in order to present to a lender.

During a presentation on Lee Arnold's Lien Abatement program they showed us a home in Spokane where a lady had her home taken over by addicts and dealers.

You could also present the deal to other local investors or private lenders who might jump at the opportunity, given the attractive terms.

Then if it grows and an opportunity presents itself in real estate then I may consider pulling the trigger on a new deal.