"This thesis contains three chapters. The first chapter investigates whether wage dynamics in long-term employment relationships can help financially constrained firms and mitigate their financial shocks. The second chapter is related to the first chapter, and investigates whether workers' wealth and liquidity conditions have any impacts on the wage dynamics when their employers face financial constraints. The third chapter studies accumulation of firm-specific human capital in the presence of debt market frictions. In chapter 1, I am motivated by the evidence which suggests financially constrained firms may offer lower wages, coupled with faster wage growth. If these constrained firms can tilt wages, cutting current wages in exchange for later increases, this potentially mitigates the impact of financial frictions or shocks. This chapter studies the aggregate implications of this mitigating effect with an application to the 2008 financial crisis. I provide a new, tractable equilibrium model of wage dynamics for heterogeneous firms--some are financially constrained, some not. Risk-neutral firms post optimal long-term wage contracts to attract risk-averse workers through competitive search. When applied to the 2008 financial crisis, the model predicts that small firms, being more likely to be constrained, tend to temporarily cut workers' wages, while for large firms wages are quite smooth and stable. Counterfactual experiments in the model show that the mitigating effect can be important. For instance, if the wages within a contract were more rigid (e.g., by raising workers' risk aversion parameter from 2 to 10), the aggregate output would have been even lower in the crisis by about 2% and the unemployment rate higher by about a third of a percentage point. Lastly, I find that the model has empirical support along several dimensions. The model is consistent with cyclical behavior in wage data (including new hires and job stayers' wage behavior). Its prediction that small firms cut wages much more than large firms is also consistent with micro-level data during the Great Recession. In chapter 2, I investigate whether workers' wealth and liquidity conditions matter for the wage dynamics in long-term employment relationships. The theoretical model in this chapter implies that wealthy workers, or workers with more liquid assets, are able to and willing to take wage adjustments when firms face financial constraints. Empirically, I find mixed evidence for this implication. For instance, among those workers who work at small firms, homeowners, compared to renters, are more likely to have wages cuts and work more hours around 2008-2009. For other measures of workers' assets and liquidity, the evidence is not significant. It is possible to explore this issue further by using richer and more detailed data, and my analysis in this chapter provides a first step toward this direction. Chapter 3 studies research and development (R&D) investment and accumulation of firm-specific knowledge capital (i.e., human capital) in the presence of debt market frictions, highlighting the macroeconomic implications. Empirically, R&D investment and knowledge capital are negatively correlated with debt at the firm level, which is in contrast with the positive relationship between physical investment and firm debt. I propose a new model to account for those facts: Firms accumulate firm-specific knowledge capital through R&D investment. However, knowledge capital-different from physical capital-cannot be used as banking collateral. Firms with high R&D investment opportunities rely more on internal finance and less on external debt. The model is quantitatively consistent with empirical facts along a variety of dimensions. Based on the model, I then study the implications of two industrial policies. A policy that encourages using intellectual property as collateral for bank loans has a small effect. I recommend a policy of tax credits for R&D investment. In fact, the tax credit policy can increase output by more than 3% in the long run."--Pages iv-vi.