Amid rising city costs to cover upgrades, repairs and upkeep of Nashville’s two main professional sports facilities, Metro government is hiring a firm that will explore the condition of both Nissan Stadium and Bridgestone Arena. The Metro Nashville Sports Authority will consider a proposal Thursday from Mayor Megan Barry’s administration to pay $355,000 to hire Venue Solutions Group, a facility management firm based in Brentwood, to carry out the assessment of both sports venues, which will include evaluating the lifespan of stadium equipment.