I could then charge the upper unit tenant $25-$30/m for wifi and that might be the extra incentive to charge $1000 for the bottom unit.

So you're trying to hold their feet to the fire for an extra month's rent and time to get the place ready.I wouldn't.

The seller is firm on the price (because seller's market and all the jazz, shark fest out there) and the house is already occupied by a renter so we can't just kick them out to do lead testing and fixing, even if we consented to pay for it out of pocket, without any extra negotiation.If we go through, we are afraid we are exposing ourselves for liability.My husband thinks this is OK - but I am chicken.Am I overreacting?

This would be my maximum as saving more would significantly take longer as I have a few cars and a motorcycle that just collect dust that I don’t need.In a perfect world I’d love to live in the available unit for free and make some extra money on the side. 

Your writings indicate your just looking to pay cash and have a propertyThe theory with brrr is you get it below market, fix it, rent it, way till it is seasoned (6-12 mos) then refinance it and get all your cash back because you have 20%+ equity in the dealAs an example I bought a condo for $70k, put $20k into it, rented it for $1500 and refinanced it as it appraised for $140k so I took a 90k loan to get my money out (don’t take extra but some may- personal preference).Now I got my 90k cash back, so no cash in deal and rent is paying PITI + condo fees and still cash flowing $200.

There are some people that have been burned bad by investing in Detroit and some only invest in Detroit because they've done so well.

I would ask myself if I could get much more than an extra $7,500 in profit by closing on it myself and then reselling it, and if not, it makes sense to get it under contract and assign. 

We added recess lighting, got the laundry inside the house, converted the extra room into a gym and also painted the whole house including the tiles in the bathroom (since me and my girlfriend were experts in painting from all the experience we had from the back house).All of this costed about $30k.

If you are further, you'll have to work hard to entice folks to drive the extra mile. 

If you continue to "train" you are only burning time because it feels productive (like in a W2 job), but if you aren't getting results, what's that worth?