That sure is a lot of questions. :-) I use software from REIWise as well as financial spreadsheets that have been passed onto me from other financial advisors to evaluate deals. I mainly work with residential rentals, so work with people who want cashflow. Some want to flip a house, which is a totally different objective.
We mainly look at the price versus comps, rental rates, after repair value, neighborhood condition, how fast homes sell in the area, schools and other local amenities, proximity to public transportation, etc. If the unit is a rental, we have to evaluate how long they plan to hold the property and who their target renter is for the area. This helps us determine the right rental amount which goes back to price...the property has to completely support itself. If not, it better be cheap enough that we can sell it for profit later.
Of course, they have to work with their CPA, lawyer, financial advisor. I give full disclaimers, but can help them gather market data. They decide on the final plan.