Help pricing renovations and a basement finish

[Travis Provin]

I am in the market for a house with either a finished or unfinished basement that I can remodel into a small apartment to househack. One thing I am struggling with is pricing out the renovations. It's one thing to price out replacing cabinets or countertops, renovating a bathroom, but it feels like a whole different beast when trying to estimate and price out finishing a basement. I am finding it difficult to run the numbers and back into an offer price I am confident in.

How does one go about doing this? I am looking at a few properties that have unfinished basements with plumbing for a utility sink already run. I would need to hire an architect and contractor to design the layout of the space, frame and insulate the walls, run electrical, run plumbing, and install egress windows. I am hoping to be able to do some of the more basic things myself like base cabinets, wall cabinets, counters and appliances for a small kitchen. Also drywall, flooring, drop ceiling, and trim myself too.

I am a first time homebuyer and at a loss to try and price out this type of work but I am in a market where I do not have the time to schedule an inspection or general contractor walk through without missing an offer deadline. Any information I am finding online is varying wildly.

How do people go about doing this?