I would encourage that you focus on houses already have finished basement for one thing that the afterward cost is "out of pocket", whereas the buying price is only, say, 20%, if you pay down that much.
Say, you got to pay $20,000 more to finish a basement to a house you pay $600,000 with 20% down, then you need to have $120k for downpayment, plus another $20k to do the work. But if you can find one with basement already finished, you pay $620,000, your upfront money is only $124k, not $140k.
Also, your money to put on basement often can not deduct income tax, whereas, your bigger mortgage interest part can offset your highest tax bracket.
As some expert says, you need to find basement with high enough ceiling, big enough ...etc, or you may have afterwards surprise while trying to finish your basement ...etc. But, if you look for house that already has finished basement, you not only save all the hassel later and what you see is what you get, less likely to regret.
Sometimes, it may not be much more expensive with finished basement.
Also, it is not always able to put bathroom in the basement, some area need to obtain permit ...etc, so if you prefer to have bath at basement and you found one already has one, you would be sure not such hassel.
When you listen realtors' advise, you need to keep in mind, they are experts, they know all sorts of contacts, laws, and procedures, but when it becomes your turn to finish a basement, you may find lots of problems and issues. Just like if you as my friend Peter worked at Toyota as senior mechenics, he shall tell you that he change oil and oil filter every 1,000 miles, and it is good for the car, and he did. He did because when I went to Toyota Avenel saw him change oil and oil filter for my Toyota Corolla 90, it only took him less than 5 minutes. The box of oil filers around looks so handy, and the oil pipe just pull from the hanging string and plug in like gas station adding oil, while he was doing other thing.
If I could change oil as if all is free and convenience, I would be glad to change every 1,000 miles, but otherwise, you may follow some dealer suggest every 3,000 miles. However, I like to read, and I read all sorts of auto manual, my Toyota manuel says, change every 7,500 miles is fine, and you know I got a Kia Sedona 2002, and the Kia manual says change every 15,000 miles, so I now change oil kind of once a year.
Ok, my sister was top 5 realtors in CA, if you ask her, she would tell you everything is so simple, not just finish basement, but finance, reconstruction ...etc. Every multi milion dollar houses could not sell come to her hand would be SOLD right away.
Why? e.g. if you love a basement for a house to be finished, she would just tell the seller, and get her construction team (yes, isnt funny, a realtor has her own construction team) to finish the basement per your needs, so, as a buyer, you would be so happy to buy the house and close when basement is finished, and seller would be glad to have hassel free selling the house, and you would just pay down extra 20% of the $20,000 cost, assuming that's the cost, rather than worrying about paying $20,000 and finish basement yourself.
I kind of go too far away, but sometimes it would help alot for people lack of experience and knowledge to make best decision. If you think you can handle finish a basement yourself, you may also want to know that cost is very different. Say, I had a bath problem, all contractors came to estimate from $600 to $1000, and when I asked how would they do, they often said that they had to knock down the wall and replace the pipe and diverter ...etc since the parts are old, need new ones, after that down, need to put back the wall, then the tiles ...etc so it is a one week job, therefore, $600 to $1,000.
Then Maria told me about Jose 732 979-9100 (cell), and he got the super of an apartment complex who was able to find the used parts of the pipe from his box of old replaced pipes, and just use many triggy tools to access the spot and replaced with a used good part, it only took 20 minutes, and costed me $10. So, do you get the idea?
Then, I get $950 to $1,700 estimate on painting a condo, but, can you believe? Jose got it painted for only $400+, thereafter, dozens of neighbors all paint their condo and got a nice shine look again; it is so affordable. So, I would say, the realtor estimate is HIGH end of the cost; it is as if just "turn key" which is wonderful, not need to worry anything, just got a contractor to take care everything, but you can see the big difference.